msm_serial_hs: Program RFR to synchronize clock-off sequence with HW

Assert the RFR line during clock off and de-assert
it after the clock off is successful. This is to avoid
the data to be coming from the client during clock off.

Change-Id: I6cad22a63ebd3cfaa20c52445584829b382b7e3a
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>