i2c: st: Rename clock reference to something that exists

CLK_S_ICN_REG_0 hasn't existed for a while now.  This was renamed
over a few commits, then finally removed in commit 5aa02b9 (ARM:
STi: DT: STiH415: Remove unused CLK_S_ICN_REG_0 fixed clock).

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Maxime Coquelin <maxime.coquelin@st.com>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-st.txt

@@ -31,7 +31,7 @@ i2c0: i2c@fed40000 {
 	compatible	= "st,comms-ssc4-i2c";
 	reg		= <0xfed40000 0x110>;
 	interrupts	=  <GIC_SPI 187 IRQ_TYPE_LEVEL_HIGH>;
-	clocks		= <&CLK_S_ICN_REG_0>;
+	clocks		= <&clk_s_a0_ls CLK_ICN_REG>;
 	clock-names	= "ssc";
 	clock-frequency = <400000>;
 	pinctrl-names	= "default";