dt-bindings: input: remove fsl-mma8450 which is handled by trivial-devices

trivial-devices.yaml already provide bindings for fsl-mma8450.
Since input/fsl-mma8450.txt provides no extra value, lets remove it.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20210521192210.12839-1-clabbe@baylibre.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>