ARM: dove: Add clock-names to CuBox Si5351 clk generator

Si5351 clock generator on CuBox uses XTAL as clock reference, name the
clock phandle accordingly.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
diff --git a/arch/arm/boot/dts/dove-cubox.dts b/arch/arm/boot/dts/dove-cubox.dts
index aae7efc..e6fa251 100644
--- a/arch/arm/boot/dts/dove-cubox.dts
+++ b/arch/arm/boot/dts/dove-cubox.dts
@@ -87,6 +87,7 @@
 
 		/* connect xtal input to 25MHz reference */
 		clocks = <&ref25>;
+		clock-names = "xtal";
 
 		/* connect xtal input as source of pll0 and pll1 */
 		silabs,pll-source = <0 0>, <1 0>;