Some BayTrail ChromeOS devices have the eMMC controller hidden (thus
requiring the use of etc/sdcard), while others do not, making it
problematic to have a single payload which serves all devices properly.
Therefore, if the CBFS contains etc/sdcard entries, skip detection of
any visible PCI sd
ROM images with a FMAP may have multiple CBFS.
Scan all available CBFS so that, say, a SeaBIOS bootable image doesn't
have to be in the main CBFS.
Coreboot puts the FMAP location in the BOOT_MEDIA_PARAMS entry in the
coreboot table. We can grab that and can all regions for CBFS files.
Signed-off-
