The RZ/G2 boards expect there to be an external clock reference for
USB2 EHCI controllers.  For the Beacon boards, this reference clock
is controlled by a programmable versaclock.  Because the RZ/G2
family has a special clock driver when using an external clock,
the third clock reference in the EHCI node needs to point to this
special clock, called usb2_clksel.

Since the usb2_clksel does not keep the usb_extal clock enabled,
the 4th clock entry for the EHCI nodes needs to reference it to
keep the clock running and make USB functional.
Signed-off-by: Adam Ford <aford173@gmail.com>
Link: https://lore.kernel.org/r/20210513114617.30191-2-aford173@gmail.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>