mmc: host: omap_hsmmc: avoid possible overflow of timeout value

Fixes: a45c6cb8 ("[ARM] 5369/1: omap mmc: Add new omap
hsmmc controller for 2430 and 34xx, v3")

when using really large timeout (up to 4*60*1000 ms for bkops)
there is a possibility of data overflow using
unsigned int so use 64 bit unsigned long long.

Signed-off-by: Ravikumar Kattekola <rk@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>