dt-bindings: arm: mstar: Add compatible for M5Stack UnitV2

Add a compatible for the M5Stack UnitV2 that is based on the
SigmaStar SSD202D (inifinity2m).

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Link: https://lore.kernel.org/r/20210417011015.2105280-3-daniel@0x0f.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/mstar/mstar.yaml

@@ -24,6 +24,7 @@ properties:
         items:
           - enum:
               - honestar,ssd201htv2 # Honestar SSD201_HT_V2 devkit
+              - m5stack,unitv2 # M5Stack UnitV2
           - const: mstar,infinity2m
 
       - description: infinity3 boards