Input: s3c24xx_ts - report touch only when stylus is down

Currently driver reports touches when it gets (1 << ts.shift) samples,
even if stylus is up, which is incorrect. We should only report coordinates
and touch condition when stylus is down.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>