tty: serial: msm: Add suspend resume support

Add suspend/resume callback support to serial msm driver.

Change-Id: I661fca45d2d762a08e331f53d8b3cb7b99117448
Signed-off-by: Pramod Gurav <gpramod@codeaurora.org>
Signed-off-by: Runmin Wang <runminw@codeaurora.org>
[Resolved conflicts in msm-serial.c]
Signed-off-by: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>