touchpad: Protect tp_begin_touch and tp_end_touch against being called twice

touchpad: Protect tp_begin_touch and tp_end_touch against being called twice

They were already protected against being called twice between SYN_REPORT, but not
for being called twice before a SYN_REPORT arrives.

This allows simplifying tp_process_fake_touch a bit. Note while at it also
also flip the if condition in tp_process_fake_touch so that the if is
true when the finger is down, and remove the bogus t->state = TOUCH_NONE.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>