ARM: dts: msm8974: Update MPM mapping to bypass uart_2_irq

Include uar_2_irq in bypass list to allow XO shutdown as this
is not wakeup-capable. uart driver has wakeup gpio on CTS pin and
optional wakeup gpio on rx pin. This should take care of wakeup
from low power state if there is any activity on the pin.

Change-Id: I10d2347eb760146b69f5b13f4cababbfcadb17bf
Signed-off-by: Girish Ghongdemath <girishsg@codeaurora.org>