mmc: msm_sdcc: perform DLL retuning if clock rate is changed

Using HS200/SDR104 bus speed mode requires DLL (Delay Locked
Loop for sampling clock generation) HW block to be tuned if
clock rate is >100MHz so that both host and card are in sync.

During card initialization, driver uses the tuning command to
search for an optimal sampling point and then programs the
DLL HW with this optimal sampling point.

But if MMC core layer switches the clock frequency to <100MHz
(when HS200/SDR104 timing mode is set) and then increases it
back to >100MHz without calling execute_tuning host ops,
DLL may go to unlocked state. So this change makes sure
that execute_tuning is performed explicitly if clock frequency
switch happens without execute_tuning.

CRs-Fixed: 424685
Change-Id: I19ee19965ca5b6a73a09f9332d34b56602051ebd
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>

Conflicts:

	drivers/mmc/host/msm_sdcc.c
	drivers/mmc/host/msm_sdcc.h

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