Input: remove atmel-wm97xx touchscreen driver

Since AVR32 arch is gone, atmel-wm97xx driver is useless. In theory it
could have been rewritten to work with AT91 devices, but the driver is from
the platform data era, and a bit hard coded to work on AVR32 hardware
variant of the AC97C peripheral, so let's remove it.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>