serial: msm_geni_serial: Modify the Rx state machine initializations

When opening the port, don't start the Rx state machine as the core clock
related configurations haven't been done at this stage.
During set_termios() operation stop and re-start the Rx state machine
before and after setting up the new baud rate.
When stopping the state machine, always try to issue a cancel on the Rx
state machine before attempting to abort the state machine and if an abort
is needed, ensure that the pad outputs are also set to the default.

CRs-Fixed: 2124301
Change-Id: I29466d14783dc2ccacaf532baa16a0900dfe0f70
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>