dt-bindings: dma: ti: k3-*: Add descriptions for register regions

In preparation for introducing more register regions, add description
for existing register regions so that its easier to map reg-names to
that of SoC Documentations/TRMs.

Signed-off-by: Vignesh Raghavendra <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/dma/ti/k3-bcdma.yaml

···
         ti,sci-rm-range-tchan: false
 
         reg:
-          maxItems: 3
+          items:
+            - description: BCDMA Control /Status Registers region
+            - description: RX Channel Realtime Registers region
+            - description: Ring Realtime Registers region
 
         reg-names:
           items:
···
     then:
       properties:
         reg:
-          minItems: 5
+          items:
+            - description: BCDMA Control /Status Registers region
+            - description: Block Copy Channel Realtime Registers region
+            - description: RX Channel Realtime Registers region
+            - description: TX Channel Realtime Registers region
+            - description: Ring Realtime Registers region
 
         reg-names:
           items:
···
         ti,sci-rm-range-bchan: false
 
         reg:
-          maxItems: 4
+          items:
+            - description: BCDMA Control /Status Registers region
+            - description: RX Channel Realtime Registers region
+            - description: TX Channel Realtime Registers region
+            - description: Ring Realtime Registers region
 
         reg-names:
           items:

Documentation/devicetree/bindings/dma/ti/k3-pktdma.yaml

···
       The second cell is the ASEL value for the channel
 
   reg:
-    maxItems: 4
+    items:
+      - description: Packet DMA Control /Status Registers region
+      - description: RX Channel Realtime Registers region
+      - description: TX Channel Realtime Registers region
+      - description: Ring Realtime Registers region
 
   reg-names:
     items:

Documentation/devicetree/bindings/dma/ti/k3-udma.yaml

···
       - ti,j721e-navss-mcu-udmap
 
   reg:
-    maxItems: 3
+    items:
+      - description: UDMA-P Control /Status Registers region
+      - description: RX Channel Realtime Registers region
+      - description: TX Channel Realtime Registers region
 
   reg-names:
     items: