dt-binding: usb: usbmisc-imx: add imx7ulp compatible

Add imx7ulp compatible
Signed-off-by: Peter Chen <peter.chen@nxp.com>

Documentation/devicetree/bindings/usb/usbmisc-imx.txt

@@ -7,6 +7,7 @@ Required properties:
 	"fsl,vf610-usbmisc" for Vybrid vf610
 	"fsl,imx6sx-usbmisc" for imx6sx
 	"fsl,imx7d-usbmisc" for imx7d
+	"fsl,imx7ulp-usbmisc" for imx7ulp
 - reg: Should contain registers location and length
 
 Examples: