Input: w90p910_ts - depend on ARCH_W90X900

The w90p910_ts touchscreen driver is heavily architecture dependent,
so there is no point in letting it be built on other architectures
than it was written for.

All other W90P910/W90X900 drivers already have that dependency, so it
makes things more consistent and configuration easier.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by Wan Zongshun <mcuos.com@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>