[PATCH] mmc: conditional scr sysfs entry

Only show the scr file in sysfs for SD cards.  Previously this was present
for all cards but had a contents of 0 for MMC cards.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>