arm64: dts: renesas: r8a774a1-hihope-rzg2m[-ex/-ex-idk-1110wr]: Rename HiHope RZ/G2M boards

The existing DTS files for HiHope RZ/G2M boards are for Rev.2.0 version
so reflect the same for the DTS file names so that the existing naming
convention can be used for Rev.3.0/4.0 boards.

While at it also added a comment about switch SW43 to be OFF for pciec1
to be activated.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Link: https://lore.kernel.org/r/1593004330-5039-2-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>