ARM: at91/dt: at91sam9261: fix clocks and clock-names in udc definition

Peripheral clock is named pclk and system clock is named hclk (those are
the names expected by the at91_udc driver).

Drop the deprecated usb_clk (formerly used to configure the usb clock rate
which is now directly configurable through hclk).
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91sam9261.dtsi

@@ -127,8 +127,8 @@ usb1: gadget@fffa4000 {
 				compatible = "atmel,at91rm9200-udc";
 				reg = <0xfffa4000 0x4000>;
 				interrupts = <10 IRQ_TYPE_LEVEL_HIGH 2>;
-				clocks = <&usb>, <&udc_clk>, <&udpck>;
-				clock-names = "usb_clk", "udc_clk", "udpck";
+				clocks = <&udc_clk>, <&udpck>;
+				clock-names = "pclk", "hclk";
 				status = "disabled";
 			};