msm8974: mhl_sii8334: disable intrs in low-pwr

Set appropriate interrupt mask to disable interrupts
in low power to prevent possible interrupt triggers
in low power mode. Enable interrupts appropriately when
chipset is brought out of low power state.

Change-Id: I267c41fd953e8afde3f157ee58228f26ee1ac20d
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>