msm_serial_hs: avoid unnecessary rx processing during port setup

Avoid unnecessary RX pipe disconnect and connect in baud rate
change function. This step is unnecessary as changing the baudrate
does not affect BAM. Configure the wakeup interrupt before the UART GPIOs
are configured to avoid spurious wakeup interrupts.

Change-Id: Ia8dc234777056ac45cfe9be211e6d987ca2378ce
Signed-off-by: Naveen Kaje <nkaje@codeaurora.org>