msm_serial_hs: Vote for Clocks

Using msm_hs_clock_vote and msm_hs_clock_unvote APIs
to enable/disable the clocks
Client can explicitly turn off the clocks while BT
is in progress without notifying to tty layer,then
TTY layer tries to access UART resulting in
un-clocked register access.As there is no notification
to TTY layer UART implicitly turns Clock ON

CRs-Fixed: 546219
Change-Id: I7a7a20992e66c562fdc1a130ced0b0973dd4dec5
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>