soc: imx: gpcv2: allow to disable individual power domains

Some board designs don't supply power to all of the power domains,
as they are not used anyways. In that case we must make sure to
not touch those power domains at all, as trying to power up a
domain that has no power supplied to it will obviously end in a
system crash. Allow to disable those domains via the standard DT
status property.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-By: Tim Harvey <tharvey@gateworks.com>
Tested-By: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>