[media] Input: move drivers/input/fixp-arith.h to include/linux

Move drivers/input/fixp-arith.h to include/linux so that the functions
defined there can be used by other subsystems, for instance some video
devices ISPs can control the output HUE value by setting registers for
sin(HUE) and cos(HUE).

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>