[PATCH v3] Add make feature support for SoCFPGA Handoff

[Sune Brian]

> You need to do some builds with "make O=/tmp/somedir". But also, I'm
> trying to make sure we avoid race conditions and that we don't try this
> logic until after the step where we know we have configured the system.

Yes this part i had agreed.

HANDOFF_PATH parameter.

```
make prepare HANDOFF_PATH=/media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0
scripts/kconfig/conf  --syncconfig Kconfig
  UPD     include/config.h
  CFG     u-boot.cfg
  GEN     include/autoconf.mk
  GEN     include/autoconf.mk.dep
  CFG     spl/u-boot.cfg
  GEN     spl/include/autoconf.mk
  UPD     include/config/uboot.release
  UPD     include/generated/version_autogenerated.h
  UPD     include/generated/timestamp_autogenerated.h
  UPD     include/generated/dt.h
  ENVC    include/generated/env.txt
  ENVP    include/generated/env.in
  ENVT    include/generated/environment.h
  HOSTCC  scripts/dtc/dtc.o
  HOSTCC  scripts/dtc/flattree.o
  HOSTCC  scripts/dtc/fstree.o
  HOSTCC  scripts/dtc/data.o
  HOSTCC  scripts/dtc/livetree.o
  HOSTCC  scripts/dtc/treesource.o
  HOSTCC  scripts/dtc/srcpos.o
  HOSTCC  scripts/dtc/checks.o
  HOSTCC  scripts/dtc/util.o
  LEX     scripts/dtc/dtc-lexer.lex.c
  YACC    scripts/dtc/dtc-parser.tab.h
  HOSTCC  scripts/dtc/dtc-lexer.lex.o
  YACC    scripts/dtc/dtc-parser.tab.c
  HOSTCC  scripts/dtc/dtc-parser.tab.o
  HOSTLD  scripts/dtc/dtc
  CC      lib/asm-offsets.s
  UPD     include/generated/generic-asm-offsets.h
  CC      arch/arm/lib/asm-offsets.s
  UPD     include/generated/asm-offsets.h
[INFO] Using manually assigned handoff path:
/media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0
Generating file: board/altera/cyclone5-socdk/qts/sdram_config.h...
Generating file: board/altera/cyclone5-socdk/qts/pinmux_config.h...
Generating file: board/altera/cyclone5-socdk/qts/pll_config.h
Reading file: /media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0/ddr3_5128x4_hps_0.hiof...
Generating file: board/altera/cyclone5-socdk/qts/iocsr_config.h...
[DONE] SoCFPGA QTS handoff conversion complete.
```

export method

```
export HANDOFF_PATH=/media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0

 make prepare
  UPD     include/config/uboot.release
  UPD     include/generated/version_autogenerated.h
  UPD     include/generated/timestamp_autogenerated.h
  UPD     include/generated/dt.h
  ENVC    include/generated/env.txt
  ENVP    include/generated/env.in
  ENVT    include/generated/environment.h
  HOSTCC  scripts/dtc/dtc.o
  HOSTCC  scripts/dtc/flattree.o
  HOSTCC  scripts/dtc/fstree.o
  HOSTCC  scripts/dtc/data.o
  HOSTCC  scripts/dtc/livetree.o
  HOSTCC  scripts/dtc/treesource.o
  HOSTCC  scripts/dtc/srcpos.o
  HOSTCC  scripts/dtc/checks.o
  HOSTCC  scripts/dtc/util.o
  LEX     scripts/dtc/dtc-lexer.lex.c
  YACC    scripts/dtc/dtc-parser.tab.h
  HOSTCC  scripts/dtc/dtc-lexer.lex.o
  YACC    scripts/dtc/dtc-parser.tab.c
  HOSTCC  scripts/dtc/dtc-parser.tab.o
  HOSTLD  scripts/dtc/dtc
  CC      lib/asm-offsets.s
  UPD     include/generated/generic-asm-offsets.h
  CC      arch/arm/lib/asm-offsets.s
  UPD     include/generated/asm-offsets.h
[INFO] Using manually assigned handoff path:
/media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0
Generating file: board/altera/cyclone5-socdk/qts/sdram_config.h...
Generating file: board/altera/cyclone5-socdk/qts/pinmux_config.h...
Generating file: board/altera/cyclone5-socdk/qts/pll_config.h
Reading file: /media/sf_shared/loader/hps_isw_handoff/ddr3_5128x4_hps_0/ddr3_5128x4_hps_0.hiof...
Generating file: board/altera/cyclone5-socdk/qts/iocsr_config.h...
[DONE] SoCFPGA QTS handoff conversion complete.
```

I think for moving to that location it leave for another patch.
I had spent time and effort already on Makefile.

I repatch this version and if there are any trouble please explain a bit to fix.

Brian