ASoC: dt-bindings: fsl,micfil: Add compatible string for imx8mp

Add compatible string for imx8mp, which has micfil module
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1652087663-1908-2-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/fsl,micfil.txt

@@ -6,6 +6,7 @@ microphone bitstream in a configurable output sampling rate.
 Required properties:
 
   - compatible		: Compatible list, contains "fsl,imx8mm-micfil"
+			  or "fsl,imx8mp-micfil"
 
   - reg			: Offset and length of the register set for the device.