drivers/mmc/core/bus.c: kmalloc + memset conversion to kzalloc

 drivers/mmc/core/bus.c | 5663 -> 5619 (-44 bytes)
 drivers/mmc/core/bus.o | 70899 -> 70731 (-168 bytes)

Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>