[media] adv7842: properly enable/disable the irqs

The method of disabling the irq-output pin caused many "empty"
interrupts. Instead, actually disable/enable the interrupts by
changing the interrupt masks.

Also enable STORE_MASKED_IRQ in INT1 configuration, otherwise when HDMI
events happen while the interrupt is masked those events will be ignored
when the interrupt is unmasked.

Signed-off-by: Martin Bugge <marbugge@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>