[media] smipcie: return more proper value in interrupt handler

Although IRQ_HANDLED is "safe" value to return,
it is better to let the kernel know whether the driver handle the interrupt or not.

Signed-off-by: Nibble Max <nibble.max@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>