arm64: dts: h3ulcb: update documentation with official board name

This updates H3ULCB Device tree bindings Documentation with
official board name
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/arm/shmobile.txt

@@ -49,7 +49,7 @@ Boards:
     compatible = "renesas,genmai", "renesas,r7s72100"
   - Gose
     compatible = "renesas,gose", "renesas,r8a7793"
-  - H3ULCB (RTP0RC7795SKB00010S)
+  - H3ULCB (R-Car Starter Kit Premier, RTP0RC7795SKB00010S)
     compatible = "renesas,h3ulcb", "renesas,r8a7795";
   - Henninger
     compatible = "renesas,henninger", "renesas,r8a7791"