mmc: sdhci: Call host ops set_clock when disabling clocks

sdhci_set_clock() has been turned into a generic library function,
all calls to change clock rate needs to call the platform specific
set_clock which will call into the generic library after performing
platform specific operations. Fix this when disabling clocks.

Change-Id: Ib01b1984291682dad709a3e38500ad31e2d3e4bc
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>