Input: tps6507x-ts - add missing call to platform_set_drvdata()

We call platform_get_drvdata() in tps6507x_ts_remove(),
thus we should call platform_set_drvdata() in tps6507x_ts_probe().

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>