mfd: mt6359: Add missing defines necessary for mtk-pmic-keys support

Add 2 missing MT6359 registers that are needed to implement
the keyboard driver.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220415153629.1817202-3-fparent@baylibre.com