ARM: dts: k2hk-netcp: add cpts refclk_mux node

KeyStone 66AK2H/K 1G Ethernet Switch Subsystems, can control an external
multiplexer that selects one of up to 32 clocks for time sync reference
(RFTCLK) clock. This feature can be configured through CPTS_RFTCLK_SEL
register (offset: x08) in CPTS module and modelled as multiplexer clock.

Hence, add cpts-refclk-mux clock node which allows to mux one of SYSCLK2,
SYSCLK3, TIMI0, TIMI1, TSREFCLK clocks as CPTS reference clock [1] and
group all CPTS properties under "cpts" subnode.

[1] http://www.ti.com/lit/gpn/66ak2h14
Signed-off-by: Grygorii Strashko <[e-mail]>
Signed-off-by: Santosh Shilimkar <[e-mail]>

arch/arm/boot/dts/keystone-k2hk-netcp.dtsi

···
 	/* NetCP address range */
 	ranges  = <0 0x2000000 0x100000>;
 
-	clocks = <&clkpa>, <&clkcpgmac>, <&chipclk12>;
-	clock-names = "pa_clk", "ethss_clk", "cpts";
+	clocks = <&clkpa>, <&clkcpgmac>;
+	clock-names = "pa_clk", "ethss_clk";
 	dma-coherent;
 
 	ti,navigator-dmas = <&dma_gbe 22>,
···
 			/* enable-ale; */
 			tx-queue = <648>;
 			tx-channel = "nettx";
+
+			cpts {
+				clocks = <&cpts_refclk_mux>;
+				clock-names = "cpts";
+
+				cpts_refclk_mux: cpts-refclk-mux {
+					#clock-cells = <0>;
+					clocks = <&chipclk12>, <&chipclk13>,
+						 <&timi0>, <&timi1>,
+						 <&tsrefclk>;
+					ti,mux-tbl = <0x0>, <0x1>, <0x2>,
+						<0x3>, <0x8>;
+					assigned-clocks = <&cpts_refclk_mux>;
+					assigned-clock-parents = <&chipclk12>;
+				};
+			};
 
 			interfaces {
 				gbe0: interface-0 {