Currently, the x86/x86_64 real-mode kernel setup code reads and stores the
mbr_signature (4 bytes in the MBR at offset 440 decimal) for BIOS int13h
device 80h only.  This is useful, but not as useful as if we stored such
signatures for all int13h devices.  Think OS installer wanting to set up md
software RAID across several BIOS disks.

Patch below against 2.6.7 allows the storing of the mbr_signature for the
first 16 BIOS int13h devices, and exports them via
/sys/firmware/edd/int13_dev8x/mbr_signature as before.

This also merges the three EXPORT_SYMBOLs that setup.c exported for edd.c's
use into one.
Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>