Input: lm8323 - convert to threaded IRQ

There's no need for that workqueue anymore. Get rid of it and move to
threaded IRQs instead.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Tested-by: Leigh Brown <leigh@solinno.co.uk>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>