serial: msm_geni_serial: Do not change Flow control from termios

This change ensures UART driver doesn't control the flow lines when
baud change is requested. UART client must ensure that peer device
is flowed off before requesting the baud change.

If UART driver control the Flow lines it may happen that after baud
rate change, immediately driver decides to Flow it ON which may have
side effect to client if it doesn't really intend to receive anything
from ther peer side.

This way we are ensuring the window of baud change is controlled by
client and not disturbed by the driver.

Change-Id: Id88ae03dc8a81830393597e72109ee7015cb6226
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>