arm64: dts: imx8mp: disable usb3_phy1

Like usb3_phy0 the default state of the usb3_phy1 should be disabled, so
it is only enabled on boards exposing this USB port.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>