dt-bindings: input: mediatek,pmic-keys: Fix typo in "linux,keycodes" property name

"linux-keycodes" is the wrong property name and is unused. It should be
"linux,keycodes" instead.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230613201040.2823802-1-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>