mmc: sdhci: Fix setting clock for HS400

The platform specific set_clock must be called even if the clock
rates are same but the timing modes are different as there may be
some platform specific handling required for different timing modes.

Change-Id: Ia7102b29a8979ad88820c60ed5874d4b2dab71a0
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>