msm_serial_hs: Handle GPIO state in PM routines

In case of OBS, the wakeup handshake is performed by an external GPIO,
outside the UART driver. In such cases, set the GPIO state appropriately
during suspend and resume operations.

Change-Id: Ibba9592e14e7983e1f6af0bd94bcdb7d5be7a9a6
Signed-off-by: Naveen Kaje <nkaje@codeaurora.org>