mmc: msm_sdcc: Add support for dynamic bus clock vote

SDCC controller on some targets like 8660, 8960, 8064 and their
variants connects with Daytona Fabric (DFAB). To achieve max.
possible performance the DFAB clock is voted to 64MHz at the
cost of some power consumption. Since we now have dynamic clock
scaling for SD/eMMC clock we can also scale the DFAB clock
accordingly without impact on performance but have some power
savings in low throughput cases.

Change-Id: Ic26541d6845b65803aa813d672ccabdfc4658d9c
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>