dt-bindings: lcdif: Document the dmas/dma-names properties

i.MX28 has an RX DMA channel associated with the LCDIF controller.

Document the 'dmas' and 'dma-names' properties to fix the following
dt-schema warnings:

lcdif@80030000: 'dma-names', 'dmas' do not match any of the regexes: 'pinctrl-[0-9]+'

Signed-off-by: Fabio Estevam <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring (Arm) <[e-mail]>

Documentation/devicetree/bindings/display/fsl,lcdif.yaml

···
       - const: disp_axi
     minItems: 1
 
+  dmas:
+    items:
+      - description: DMA specifier for the RX DMA channel.
+
+  dma-names:
+    items:
+      - const: rx
+
   interrupts:
     items:
       - description: LCDIF DMA interrupt
···
       properties:
         interrupts:
           maxItems: 1
+
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - fsl,imx28-lcdif
+    then:
+      properties:
+        dmas: false
+        dma-names: false
 
 examples:
   - |