arm64: dts: sprd: Add clock properties for serial devices

We've introduced power management logics for the Spreadtrum serial
controller by commit 062ec2774c8a ("serial: sprd: Add power management
for the Spreadtrum serial controller"), thus add related clock properties
to support this feature.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm64/boot/dts/sprd/whale2.dtsi

@@ -75,7 +75,9 @@ uart0: serial@0 {
 					     "sprd,sc9836-uart";
 				reg = <0x0 0x100>;
 				interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&ext_26m>;
+				clock-names = "enable", "uart", "source";
+				clocks = <&apapb_gate CLK_UART0_EB>,
+				       <&ap_clk CLK_UART0>, <&ext_26m>;
 				status = "disabled";
 			};
 
@@ -84,7 +86,9 @@ uart1: serial@100000 {
 					     "sprd,sc9836-uart";
 				reg = <0x100000 0x100>;
 				interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&ext_26m>;
+				clock-names = "enable", "uart", "source";
+				clocks = <&apapb_gate CLK_UART1_EB>,
+				       <&ap_clk CLK_UART1>, <&ext_26m>;
 				status = "disabled";
 			};
 
@@ -93,7 +97,9 @@ uart2: serial@200000 {
 					     "sprd,sc9836-uart";
 				reg = <0x200000 0x100>;
 				interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&ext_26m>;
+				clock-names = "enable", "uart", "source";
+				clocks = <&apapb_gate CLK_UART2_EB>,
+				       <&ap_clk CLK_UART2>, <&ext_26m>;
 				status = "disabled";
 			};
 
@@ -102,7 +108,9 @@ uart3: serial@300000 {
 					     "sprd,sc9836-uart";
 				reg = <0x300000 0x100>;
 				interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&ext_26m>;
+				clock-names = "enable", "uart", "source";
+				clocks = <&apapb_gate CLK_UART3_EB>,
+				       <&ap_clk CLK_UART3>, <&ext_26m>;
 				status = "disabled";
 			};
 		};