board-8064: Correct UART GPIO IRQ to use as wakeup IRQ

IRQ for UART RX GPIO is wakeup source to MSM. Currently UART TX
GPIO's IRQ is configured as wakeup IRQ. With that APQ UART is not
receiving any wakeup when connected external modem is sending wakeup
byte. Hence correct the same by configuring UART RX GPIOs' IRQ line
as wakeup IRQ.

CRs-Fixed: 473028
Change-Id: I3df56f9eb0dd2f4dcb4f17f6819338e46bd313dd
Signed-off-by: Mayank Rana <mrana@codeaurora.org>