serial: msm_geni_serial: Pull RFR before stop_rx for uart

Pull the RFR line before doing stop_rx in uart driver.
This is to prevent any rx data to come into the uart rx fifo when
stop_rx is being done.

Change-Id: I92163c4997c1709269dce67a1d492533f710abfb
Signed-off-by: Prudhvi Yarlagadda <pyarlaga@codeaurora.org>