Input: wm97xx - switch to using threaded IRQ

Instead of manually disabling and enabling interrupts and scheduling work
to access the device, let's use threaded oneshot interrupt handler. It
simplifies things.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>