Input: mms114 - mark as direct input device

mms14 is a touchscreen and thus a direct input device; let's mark it
as such. This also allows us to drop some initialization code as
input_init_mt_slots() will do that for us.

Also add error handling for input_mt_init_slots().

Reviewed-by: Simon Shields <simon@lineageos.org>
Tested-by: Simon Shields <simon@lineageos.org>
Reviewed-by: Andi Shyti <andi.shyti@samsung.com>
Tested-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>