MAINTAINERS: add include/dt-bindings/input to INPUT DRIVERS

Maintainers of the directory Documentation/devicetree/bindings/input
are also the maintainers of the corresponding directory
include/dt-bindings/input.

Add the file entry for include/dt-bindings/input to the appropriate
section in MAINTAINERS.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220613115654.28117-1-lukas.bulwahn@gmail.com


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