arm64: dts: renesas: white-hawk: Add SoC name to top-level comment

The White Hawk CPU and BreakOut board DTS is specific to R-Car V4H.
Document it in the top-level comment.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/de81db7ca38c8f4737092bdac6891e9db4bb9bd6.1706192990.git.geert+renesas@glider.be

arch/arm64/boot/dts/renesas/r8a779g0-white-hawk.dts

 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /*
- * Device Tree Source for the White Hawk CPU and BreakOut boards
+ * Device Tree Source for the R-Car V4H White Hawk CPU and BreakOut boards
  *
  * Copyright (C) 2022 Renesas Electronics Corp.
  */