arm64: dts: renesas: beacon: Fix USB extal reference

The USB extal clock reference isn't associated to a crystal, it's
associated to a programmable clock, so remove the extal reference,
add the usb2_clksel.  Since usb_extal is referenced by the versaclock,
reference it here so the usb2_clksel can get the proper clock speed
of 50MHz.
Signed-off-by: Adam Ford <aford173@gmail.com>
Link: https://lore.kernel.org/r/20210513114617.30191-1-aford173@gmail.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm64/boot/dts/renesas/beacon-renesom-som.dtsi

@@ -321,8 +321,10 @@ &sdhi3 {
 	status = "okay";
 };
 
-&usb_extal_clk {
-	clock-frequency = <50000000>;
+&usb2_clksel {
+	clocks = <&cpg CPG_MOD 703>, <&cpg CPG_MOD 704>,
+		  <&versaclock5 3>, <&usb3s0_clk>;
+	status = "okay";
 };
 
 &usb3s0_clk {