msm_serial_hs: Configure UART RX gpio line as wakeup irq line

UART wakeup can be triggered by RX activity using a wakeup GPIO on the
UART RX pin. This change adds support for configuring the UART RX gpio
line as wakeup irq line.

CRs-Fixed: 482104
Change-Id: I775c17d4d36b08225b32063131473567c2d16f9c
Signed-off-by: Saket Saurabh <ssaurabh@codeaurora.org>
Signed-off-by: Ram Mohan Korukonda <rkorukon@codeaurora.org>