arm64: defconfig: enable Mediatek PMIC key

arm64: defconfig: enable Mediatek PMIC key

Some Mediatek PMIC devices can manage Power and Home keys (buttons).
This patch enable the driver which handle the 2 keys managed by the
Mediatek PMIC.

Tested-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://lore.kernel.org/r/20230203-evk-board-support-v8-2-7019f3fd0adf@baylibre.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>