app: aboot: Fix fastboot boot issue.

Calling get_ffbm from the update_cmdline function caused the boot
image present at the scratch address to get corrupted which in turn
caused fastboot boot to fail. We now call get_ffbm only if we are booting
the kernel from the emmc.

Change-Id: Ie2efece5b82ed7d5414a1be80f10779c2e63c0d2
3 files changed