mmc: Fix compile for omap_hsmmc.c

This fixes the issue noted by Russell King:

drivers/mmc/host/omap_hsmmc.c: In function 'mmc_omap_xfer_done':
drivers/mmc/host/omap_hsmmc.c:301: error: implicit declaration of function 'mmc_omap_fclk_lazy_disable'

This got broken by 4a694dc9.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Pierre Ossman <pierre@ossman.eu>