[PATCH 2/2] arm: mvebu: clearfog: Add defconfig for SPI booting

[Martin Rowe]

> While I haven't tested this patchset - I have tested SPI booting with v2022.01 after applying lots of patches.
> I found that the magic value reported by bootrom when booting from SPI will be 0x34 on clearfog.
> The current sources only handle 0x32, hence having or not having SPL_SPI will always lead to returning to the bootrom.
>
> Please consider pulling in this patch:
> https://github.com/SolidRun/u-boot/commit/f4f8a69740a8415c05359e01e51650f445cda03d
> I can send it separately if you like.

Tested with the patch on a Clearfog Base:
================== Without SPL_SPI same return to BootROM
...
mv_ddr: completed successfully
Trying to boot from BOOTROM
Returning to BootROM (return address 0xffff05c4)...
BootROM: Image checksum verification PASSED


U-Boot 2023.04-rc2...
================== With SPL_SPI loads directly from SPI
...
mv_ddr: completed successfully
Trying to boot from SPI


U-Boot 2023.04-rc2...
==================

I'm not sure how to run proper timing tests on the process, but
stopwatch timing just between seeing "Trying to boot" and "U-Boot
2023.04-rc2" showed the return to BootROM under 1 second, and the
direct from SPI around 4 seconds. I thought the goal of loading from
SPI directly was speed, but returning to BootROM is significantly
faster on this board.

> which I have tested by adding these config options:

I tested the new spi_defconfig with and without SPL_SPI; no other changes