Input: wm97xx - get rid of irq_enable method in wm97xx_mach_ops

Now that we are using oneshot threaded IRQ this method is not used anymore.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[arnd: add the db1300 change as well]
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>