clk: imx8mp: Add missing IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT clock

clk: imx8mp: Add missing IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT clock

The IMX8MP_CLK_MEDIA_MIPI_PHY1_REF_ROOT clock derives from the
media_mipi_phy1_ref clock and is gated by the shared media clock gate.
Its identifier is defined in dt-bindings/clock/imx8mp-clock.h but its
definition is missing from the driver. Add it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Link: https://lore.kernel.org/r/20220211091311.28146-1-laurent.pinchart@ideasonboard.com
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>