msm_serial_hs: Access hardware with clocks on during port close

The clients can close the port after issuing a clock
off request. Ensure that clocks are turned on before
accessing dependant hardware resources.

Change-Id: I31c71855569dc186bb2b8f5a5322ca7f34ea21bd
Signed-off-by: Naveen Kaje <nkaje@codeaurora.org>