ARM: dts: imx6sll: declare src module to be compatible to imx51's src

i.MX6SLL uses same SRC module as i.MX51, add "fsl,imx51-src"
compatible string to enable SRC driver to support setting
CPU resume address for cpu-idle and suspend/resume.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6sll.dtsi

@@ -548,7 +548,7 @@ snvs_pwrkey: snvs-powerkey {
 			};
 
 			src: reset-controller@20d8000 {
-				compatible = "fsl,imx6sll-src";
+				compatible = "fsl,imx6sll-src", "fsl,imx51-src";
 				reg = <0x020d8000 0x4000>;
 				interrupts = <GIC_SPI 91 IRQ_TYPE_LEVEL_HIGH>,
 					     <GIC_SPI 96 IRQ_TYPE_LEVEL_HIGH>;