mmc: omap_hsmmc: build fix for CONFIG_OF=y and CONFIG_MMC_OMAP_HS=m

Commit 46856a68

 ("mmc: omap_hsmmc: Convert hsmmc driver to use device tree")
introduced in 3.4-rc1 has a missing semi-colon, causing:

drivers/mmc/host/omap_hsmmc.c:1745: error: expected ',' or ';' before 'extern'

Reported-by: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Chris Ball <cjb@laptop.org>