staging: dt3155v4l: remove irq_handler from struct dt3155_priv

There is no reason to cache the irq_handler in struct dt3155_priv.  Just pass
the function directly in request_irq.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>