ARM: dts: Include R-Car Gen1 product name in DTSI files

Browsing the DTS for all the R-Car SoCs with similar part numbers
still makes my head hurt, so to improve the user friendliness of
the 32-bit ARM DTS code base include R-Car Gen1 product names for
each DTSI file.
Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7778.dtsi

 // SPDX-License-Identifier: GPL-2.0
 /*
- * Device Tree Source for Renesas r8a7778
+ * Device Tree Source for the R-Car M1A (R8A77781) SoC
  *
  * Copyright (C) 2013  Renesas Solutions Corp.
  * Copyright (C) 2013  Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

arch/arm/boot/dts/r8a7779.dtsi

 // SPDX-License-Identifier: GPL-2.0
 /*
- * Device Tree Source for Renesas r8a7779
+ * Device Tree Source for the R-Car H1 (R8A77790) SoC
  *
  * Copyright (C) 2013 Renesas Solutions Corp.
  * Copyright (C) 2013 Simon Horman