mmc: sdhci-msm: Vote for MSM bus clocks before enabling iface_clk

The current driver just enables "iface_clk" before accessing its
registers but MSM bus clocks are also required for register access
without which any register access would result in chip reset.

The MSM bus clocks can be enabled by setting vote to MSM bus bandwidth
driver. Currently, voting is being done in sdhci_enable/disable but these
functions will not be invoked by MMC core layer for some cases such
as mmc_power_up/mmc_power_off, which require peripheral register
access.

To resolve the above mentioned problem, bus voting and de-voting will
now be done as part of clock management within the sdhci MSM driver
i.e., before enabling SDHC clocks and after disabling SDHC clocks.

Change-Id: Iff608fba4c58bf37a6f4ce8eb36876c79969feaf
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>