memstick: add support for 8-bit parallel mode

Newer MemoryStick (HG) cards and hosts support 8-bit parallel mode of
operation in addition to original 4-bit and 1-bit modes.

Signed-off-by: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>