[media] v4l: omap4iss: Enhance IRQ debugging

Add a pretty print function for ISP IRQs and remove the _INT suffix from
interrupt names to enhance readability.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>