mmc: sdhci-msm: Support for getting DLL HSR values from dt file

This is a porting of commit <d44b7d92b3>.
Add support for getting dll hsr setting from device tree file and
to update the dll registers with these HSR settings.

HSR(Hardware Settings Reference) values of DLL specific registers in
SDHC controller would vary based on the process node. Getting these
values through device tree ensure the driver is agnostic of process
node changes.

Use actual clock instead of standard clock rate while configuring DLL
frequency. Otherwise, DLL frequency doesn't match with recommended
HSR value.

With this changes DDR config dt property redundant. So deleting it.

Change-Id: I1e8e1b673c91c2229b979b7a59d89bb5f79ed1cc
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>