mtd: sm_common: split smartmedia and xD table

2GB xD card, and 4MB SmartMedia ROM card share same ID, so to make both work
split xD and smartmedia ID tables.

Hardware driver must be able to know which type it handles (and probably just one).

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>