arm64: dts: broadcom: bcm4908: Fix UART clock name

According to the binding the correct clock name is "refclk".

Fixes: 2961f69f ("arm64: dts: broadcom: add BCM4908 and Asus GT-AC5300 early DTS files")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm64/boot/dts/broadcom/bcm4908/bcm4908.dtsi

@@ -292,7 +292,7 @@ uart0: serial@640 {
 			reg = <0x640 0x18>;
 			interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&periph_clk>;
-			clock-names = "periph";
+			clock-names = "refclk";
 			status = "okay";
 		};