V4L/DVB (6065): cx88-alsa: Call core irq handler when needed

When an irq handled by the cx88 core driver (currently IR and errors) occurs
and the cx88-alsa irq handler is the first called, it will claim to have
handled the irq but it doesn't call cx88_core_irq() to handle it.

The means loading cx88-alsa can disable the IR remote.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>