Input: ar1021_i2c - do not force raising edge IRQ trigger

We should not be forcing edge triggered interrupt, but rather let platform
decide the kind of trigger it needs to use. Also, the driver is not quite
safe with regard to edge-triggered interrupts as it does not try to kick
the controller after requesting/enabling IRQ.

Reviewed-By: Christian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>