dt-bindings: mmc: fsl-imx-esdhc: add imx8qm compatible string

Add imx8qm compatible string.
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt

@@ -21,6 +21,7 @@ Required properties:
 	       "fsl,imx8mq-usdhc"
 	       "fsl,imx8mm-usdhc"
 	       "fsl,imx8mn-usdhc"
+	       "fsl,imx8qm-usdhc"
 	       "fsl,imx8qxp-usdhc"
 
 Optional properties: