Revert "HID: multitouch: enable palm rejection if device implements confidence usage"

This reverts commit 25a84db1 ("HID: multitouch: enable palm rejection
if device implements confidence usage")

The commit enables palm rejection for Win8 Precision Touchpad devices but
the quirk MT_QUIRK_VALID_IS_CONFIDENCE it is using is not working very
properly. This quirk is originally designed for some WIn7 touchscreens. Use
of this for a Win8 Precision Touchpad will cause unexpected pointer jumping
problem.

Cc: stable@vger.kernel.org # v4.5+
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Tested-by: Andy Lutomirski <luto@kernel.org> # XPS 13 9350, BIOS 1.4.3
Signed-off-by: Allen Hung <allen_hung@dell.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>