Input: mtk-pmic-keys - add support for MT6331 PMIC keys

Add support for PMIC Keys of the MT6331 PMIC.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20220913123941.385349-1-angelogioacchino.delregno@collabora.com


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