mmc: host: Register changes for sdcc V5

Add support to use the new compatible string "qcom,sdhci-msm-v5".

Based on the msm variant, pick the relevant variant data and
use it for register read/write to msm specific registers.

Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>
Reviewed-by: Evan Green <evgreen@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>