media: cec-pin: improve interrupt handling

The CEC pin framework needs a bit more control over the interrupt
handling: make sure that the disable_irq op is called even if the
device node is unregistered, log the state of the interrupt in
debugfs, and disable the interrupt when the kernel thread is stopped.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>