[PATCH u-boot v2019.04-aspeed-openbmc] configs: Add OpenBMC spl defconfig for AST2600 boards

[Adriana Kobylak]

>> +CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR=y
>> +CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x0
>> +CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION=y
> 
> How do these work? I thought the SPL loaded u-boot.bin from SPI NOR
> for now. Do we need to change these?

It appears these were added to the ast2600 defconfig to reduce the size 
of the SPL:
https://github.com/openbmc/u-boot/commit/688ce7568eaffec782fe451ac807961f9abf4e19

Even with these enabled the SPL loads the u-boot.bin from the SPI NOR.
Perhaps a setting for MMC in raw mode is equivalent to the raw NOR 
partition.

> 
> How should we handle the configuration options when we want to build a 
> eMMC SPL?
> 

I'd say we can create a separate "mmc" defconfig.