clk: shmobile: cpg-mssr: Update serial port clock in example

Cfr. commit a9ec81f4 ("serial: sh-sci: Drop the interface
clock").
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: NMichael Turquette <mturquette@baylibre.com>

Documentation/devicetree/bindings/clock/renesas,cpg-mssr.txt

@@ -61,7 +61,7 @@ Examples
 		reg = <0 0xe6e88000 0 64>;
 		interrupts = <GIC_SPI 164 IRQ_TYPE_LEVEL_HIGH>;
 		clocks = <&cpg CPG_MOD 310>;
-		clock-names = "sci_ick";
+		clock-names = "fck";
 		dmas = <&dmac1 0x13>, <&dmac1 0x12>;
 		dma-names = "tx", "rx";
 		power-domains = <&cpg>;