msm_serial_hs_lite: Handle Tx request during System Suspend

A corner case is occuring, that performing un-clock register
access and leading to Kernel Crash
Corner Case:
When system is in suspend state, Tx operation is getting called
from the client driver by a fflush system call.
To overcome this case, added a conditional check in the driver
while Tx operation. If system is in suspend state, return back
immediately.

CRs-Fixed: 570113
Change-Id: Idab06cbb49610dd36146fd22714ef20c63000ba5
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>