arm64: dts: imx8qxp-ss-adma: Drop fsl,imx7ulp-lpuart comaptible

The driver differs from clocks point of view, so the i.MX8QXP
is not backwards compatible with i.MX7ULP.
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8qxp-ss-adma.dtsi

@@ -5,19 +5,19 @@
  */
 
 &lpuart0 {
-	compatible = "fsl,imx8qxp-lpuart", "fsl,imx7ulp-lpuart";
+	compatible = "fsl,imx8qxp-lpuart";
 };
 
 &lpuart1 {
-	compatible = "fsl,imx8qxp-lpuart", "fsl,imx7ulp-lpuart";
+	compatible = "fsl,imx8qxp-lpuart";
 };
 
 &lpuart2 {
-	compatible = "fsl,imx8qxp-lpuart", "fsl,imx7ulp-lpuart";
+	compatible = "fsl,imx8qxp-lpuart";
 };
 
 &lpuart3 {
-	compatible = "fsl,imx8qxp-lpuart", "fsl,imx7ulp-lpuart";
+	compatible = "fsl,imx8qxp-lpuart";
 };
 
 &i2c0 {