MLK-14638-2 ARM: dts: add off-on-delay for usdhc vmmc-supply regulator

MLK-14638-2 ARM: dts: add off-on-delay for usdhc vmmc-supply regulator

For the slot support SD3.0 card, during system suspend, if plug out
the sd card, and insert another SD3.0 card, after system resume back,
SD3.0 card can't be recognised as SD3.0 card, just SD2.0 card.

This is bause the time delay between vmmc regulator off and on is
too small, this patch add the oo-on-delay in vmmc-supply regulator,
to assign proper delay value.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>