mmc: msm_sdcc: fix voltage switch handling

With commit 0797e5f1 (mmc: core: Fixup signal voltage switch), most of
the voltage switch sequence handling is moved to MMC core framework layer
and hence the role of host controller driver is left only to provide few
callbacks (one callback to change the voltage level and one more to let
the core layer know whether the card is puling down the data lines or
not).

This patch makes all the relevant changes to msm_sdcc host controller
driver to make it work with updated MMC core framework layer.

Change-Id: Ia1620ae351318cffbc58b03988ee815c66ed80df
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>