mmc: sdhci-msm: adapt to allow drop-in use in place of downstream driver

In order for this driver to function as a drop-in replacement for the
msm-3.10 driver:

  - Allow selectability on ARCH_MSM
  - Rename clock names to include _clk prefix
  - Change supported compatible string

Change-Id: I20bc683512ebdd22fcd7845c7e43dd645a2f146f
Signed-off-by: Georgi Djakov <gdjako@codeaurora.org>
Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
[xiaonian@codeaurora.org: fix trivial merge conflict]
Signed-off-by: Xiaonian Wang <xiaonian@codeaurora.org>