ASoC: mchp,i2s-mcc: Add SAMA7G5 to binding

SAMA7G5 includes an updated version of the I2S-MCC driver, that includes
3 more DIN/DOUT pin pairs for multi-channel.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20210301170905.835091-2-codrin.ciubotariu@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/mchp-i2s-mcc.txt

 * Microchip I2S Multi-Channel Controller
 
 Required properties:
-- compatible:     Should be "microchip,sam9x60-i2smcc".
+- compatible:     Should be "microchip,sam9x60-i2smcc" or
+		  "microchip,sama7g5-i2smcc".
 - reg:            Should be the physical base address of the controller and the
                   length of memory mapped region.
 - interrupts:     Should contain the interrupt for the controller.