serial: msm_geni_serial: Modify power off sequence

For HS-UART devices, the userspace drivers control powering on/off the
port.
When these requests come in too frequently ping-ponging the port between
on and off states in quick succession can put the receive state machine of
the port in a bad state aborting/corrupting the received data.
Use delayed power-off to compensate for these cases.  Write the RX
packing and stale timeout registers only once during port setup and not
constantly during port open/close.
Also reject packets where framing/parity errors are detected.

Change-Id: Ib3e9feff5cfc12ef72d74b8f4085412c66c33b5b
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>