ARM: dts: imx: correct sdma compatbile for imx6sl and imx6sx

The SDMA on imx6sl and imx6sx is more compatible with imx6q one than
imx35. Let's use "fsl,imx6q-sdma" instead of "fsl,imx35-sdma", so that
SDMA ROM script on imx6sl and imx6sx can work for audio driver just like
the case of imx6q.

Reported-by: Fabio Estevam <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>
Acked-by: Robin Gong <[e-mail]>

arch/arm/boot/dts/imx6sl.dtsi

···
 			};
 
 			sdma: sdma@020ec000 {
-				compatible = "fsl,imx6sl-sdma", "fsl,imx35-sdma";
+				compatible = "fsl,imx6sl-sdma", "fsl,imx6q-sdma";
 				reg = <0x020ec000 0x4000>;
 				interrupts = <0 2 IRQ_TYPE_LEVEL_HIGH>;
 				clocks = <&clks IMX6SL_CLK_SDMA>,

arch/arm/boot/dts/imx6sx.dtsi

···
 			};
 
 			sdma: sdma@020ec000 {
-				compatible = "fsl,imx6sx-sdma", "fsl,imx35-sdma";
+				compatible = "fsl,imx6sx-sdma", "fsl,imx6q-sdma";
 				reg = <0x020ec000 0x4000>;
 				interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
 				clocks = <&clks IMX6SX_CLK_SDMA>,