mmc: msm_sdcc: minimum card clock selection

If card clock rate passed by set_ios() is less than
minimum clock rate supported by the host controller,
set the clock rate to minimum clock rate supported by host.

Change-Id: I22f2a7413dfdb8c9a5188992aed99726c3c3d7a7
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>