[U-Boot] Clearfog fails to build with U-Boot v2018.07-rc1

[guillaume.gardet at free.fr]

Hi Stefan,

Clearfog config fails to build with U-Boot v2018.07-rc1, because SPL is too big:

    LD      spl/u-boot-spl
  ld.bfd: SPL image too big
  make[1]: *** [scripts/Makefile.spl:347: spl/u-boot-spl] Error 1
  make: *** [Makefile:1510: spl/u-boot-spl] Error 2

Guillaume