dt-bindings: usb: do not use deprecated synopsys prefix

The "synopsys" prefix and "synopsys,dwc3" compatible are deprecated.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/usb/dwc3-cavium.txt

···
 			    refclk-type-hs = "dlmc_ref_clk0";
 			    power = <0x00000002 0x00000002 0x00000001>;
 			    xhci@1690000000000 {
-				    compatible = "cavium,octeon-7130-xhci", "synopsys,dwc3";
+				    compatible = "cavium,octeon-7130-xhci", "snps,dwc3";
 				    reg = <0x00016900 0x00000000 0x00000010 0x00000000>;
 				    interrupt-parent = <0x00000010>;
 				    interrupts = <0x00000009 0x00000004>;

Documentation/devicetree/bindings/usb/ti,keystone-dwc3.yaml

···
       ranges;
 
       usb@2690000 {
-        compatible = "synopsys,dwc3";
+        compatible = "snps,dwc3";
         reg = <0x2690000 0x70000>;
         interrupts = <GIC_SPI 393 IRQ_TYPE_EDGE_RISING>;
         usb-phy = <&usb_phy>, <&usb_phy>;