HID: multitouch: Add memory barriers

HID: multitouch: Add memory barriers

commit be6e2b5734a425941fcdcdbd2a9337be498ce2cf upstream.

This fixes broken atomic checks which cause a race between the
release-timer and processing of hid input.

I noticed that contacts were sometimes sticking, even with the "sticky
fingers" quirk enabled. This fixes that problem.

Cc: stable@vger.kernel.org
Fixes: 9609827458c3 ("HID: multitouch: optimize the sticky fingers timer")
Signed-off-by: Andri Yngvason <andri@yngvason.is>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20220907150159.2285460-1-andri@yngvason.is
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>