mmc: sdhci-of-dwcmshc: add SDHCI OF Synopsys DWC MSHC driver

Add a driver for SDHCI OF Synopsys DesignWare Cores Mobile Storage

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>