Input: MT - add INPUT_MT_TOTAL_FORCE flags

Input: MT - add INPUT_MT_TOTAL_FORCE flags

Add a flag to generate ABS_PRESSURE as sum of ABS_MT_PRESSURE across
all slots.
This flag should be set if one knows a device reports true force and would
like to report total force to the userspace.

Signed-off-by: Angela Czubak <aczubak@google.com>
Co-developed-by: Jonathan Denose <jdenose@google.com>
Signed-off-by: Jonathan Denose <jdenose@google.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>