mmc: sdhci-msm: set the clock rate before enabling it

The drivers must do clk_set_rate() before the first
clk_prepare_enable() is invoked. Otherwise, the clock
driver may give a warning for such clocks.

CRs-fixed: 493685
Change-Id: I8342aa2f35d64a4dc7b8396bd9741c0aecaedc5c
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>