drivers/mmc/host/sdhci.h needs scatterlist.h

alpha:

drivers/mmc/host/sdhci.h:242: error: field 'sg_miter' has incomplete type

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