serial: msm_geni_serial: Avoid manual RFR flow control for OBS

Currently UART driver making RFR to LOW during UART suspend.
In issue case external SOC is used with Out of band sleep(OBS) and
as RFR is low from UART SOC is trying to send RX data when UART
is in sleep state and leading to RX packet loss.

Fix this issue by avoiding manual RFR flow control feature for
OBS case.

Change-Id: Id9ee9cc48924bf8b70d580c7878cfdd164ed6b37
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>