ARM: dts: imx7: Move hsic_phy power domain to HSIC PHY node

Move the power domain to its actual user. This keeps the power domain
enabled even when the USB host is runtime suspended. This is necessary
to detect any downstream events, like device attach.

Fixes: 02f8eb40 ("ARM: dts: imx7s: Add power domain for imx7d HSIC")
Suggested-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>