[coreboot] [PATCH]More helpful error if cbfs header magic is 0xffffffff

[Patrick Georgi]

Hi,

attached patch hopefully helps track down issues related to late 
enable_rom calls.
If the CBFS header magic is 0xffffffff, chances are that this is because 
the lower parts of the ROM aren't mapped yet. Point to 
http://www.coreboot.org/Infrastructure_Projects#CBFS, which provides 
some description and a nice table (Thanks Uwe!) about the current status.

Signed-off-by: Patrick Georgi