arm64: dts: ipq6018: Use reference clock to set dwc3 period

Instead of manually setting snps,ref-clock-period-ns, we can let the
driver calculate it automatically from the "ref" clock. I haven't
reviewed this board's schematics, so please let me know if this is the
wrong 24MHz clock to use.
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/20220127200636.1456175-8-sean.anderson@seco.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/arm64/boot/dts/qcom/ipq6018.dtsi

@@ -743,12 +743,13 @@ dwc_0: usb@8A00000 {
 				interrupts = <GIC_SPI 140 IRQ_TYPE_LEVEL_HIGH>;
 				phys = <&qusb_phy_0>, <&usb0_ssphy>;
 				phy-names = "usb2-phy", "usb3-phy";
+				clocks = <&xo>;
+				clock-names = "ref";
 				tx-fifo-resize;
 				snps,is-utmi-l1-suspend;
 				snps,hird-threshold = /bits/ 8 <0x0>;
 				snps,dis_u2_susphy_quirk;
 				snps,dis_u3_susphy_quirk;
-				snps,ref-clock-period-ns = <0x32>;
 				dr_mode = "host";
 			};
 		};