phy: phy-stih41x-usb: DT spelling s/#phy-cell/#phy-cells/

Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/phy-stih41x-usb.txt

@@ -17,7 +17,7 @@ Example:
 
 usb2_phy: usb2phy@0 {
 	compatible	= "st,stih416-usb-phy";
-	#phy-cell	= <0>;
+	#phy-cells	= <0>;
 	st,syscfg	= <&syscfg_rear>;
 	clocks		= <&clk_sysin>;
 	clock-names	= "osc_phy";