Input: ads7846 - avoid pen up/down when reading hwmon

Each time the HWMON devices are read (e.g. battery voltage) while the
touchscreen is held pressed, extra pen-up and pen-down events are
generated. This is fixed by avoiding the UP event when the touchscreen is
stopped.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>