[U-Boot] Falcon boot breaks on DRA7 because of commit b9c8ccab "env_mmc.c: Allow environment to be used within SPL"

[Jean-Jacques Hiblot]

Hi Tom,

I'm using a TI DRA7 platform and the falcon boot from MMC is broken with 
v2017. The reason is that the standard "boot_os" is used to tell whether 
the falcon mode should be used or not, but we can't access it. The root 
cause is that the environment is stored in a eMMC which is dev 1 not dev 
0 on those platforms.

What is the purpose of commit b9c8ccab. Is it because we want to 
initialize only one MMC device in the SPL to reduce the boot time ?

Jean-Jacques