adv7481: Fix interrupt handling

ADV7481 raises back-to-back interrupts on cable connect and
disconnect. The IRQ bottom half has to check the interrupt status
register in a loop and service all events that have been raised,
rather than relying on the top half getting scheduled for each event.

Signed-off-by: Jaiju Yesudasan <cjaijuy@codeaurora.org>
Change-Id: I388d951fa5ed8ac22db9358e86de74d0b83c5a50