mmc: sdhci-msm: Read and use DDR Config property from dt file

Certain platforms require different settings in the
SDCC_HC_REG_DDR_CONFIG register. This setting can change from platform
to platform. So the driver should check whether a particular platform
require a different setting by reading the DT file and use it.

Change-Id: I357ecb8c87b573ea94bac2adc5b997d13def57ef
Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>