[media] lirc_zilog: Update IR Rx polling kthread start/stop and some printks

[media] lirc_zilog: Update IR Rx polling kthread start/stop and some printks

The IR Rx polling thread was originally a kernel_thread long ago,
and had only been minimally converted to a kthread.  This patch
finishes that conversion by

- cleaning up all the unneeded completions

- destroying the kthread properly by calling kthread_stop()

- changing lirc_thread() to test kthread_should_stop() just before
	every point where it may sleep

- reorganizing the lirc_thread() function so it uses fewer lines

- modifying the name of the kthread from "lirc_zilog" to
	"zilog-rx-i2c-N", so ps will show which kthread polls
	which Zilog Z8 IR unit.

Also some minor tweaks were made to logging emitted by the
ir_probe() function.

Signed-off-by: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>