serial: msm_geni_serial: Enable SW flow on in runtime suspend

Stop_rx is bailing out in the runtime suspend path because of
parallel data from SOC and there is no SW  FLOW ON from UART,
causing SOC unable to send RX data to host.

Enabled SW flow on if the stop_rx is bailing out during
runtime suspend.

Change-Id: I0dd52fafe99466e6177a60a108132f25a5be570b
Signed-off-by: Yatish Kumar Singh <yatishku@codeaurora.org>