regulator: max77620: add support to configure MPOK

Adding support to configure regulator POK mapping bit
to control nRST_IO and GPIO1 POK function.
In  tegra based platform which uses MAX20024 pmic, when
some of regulators are configured FPS_NONE(flexible power sequencer)
causes PMIC GPIO1 to go low which lead to various other rails turning off,
to avoid this MPOK bit of those regulators need to be set to 0
so that PMIC GPIO1 will not go low.

Signed-off-by: Venkat Reddy Talla <vreddytalla@nvidia.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>