dt-bindings: soc: renesas: Document R-Car R8A779MD Geist

dt-bindings: soc: renesas: Document R-Car R8A779MD Geist

Document the compatible value for the Renesas R-Car M3Le (R8A779MD)
SoC and the Renesas Geist development board.  The Renesas M3Le SoC is
a register-compatible variant of the R8A77965 (M3-N) with reduced set
of peripherals.  The Geist board is derived from Renesas Salvator-X/XS
boards, with adjustment for the R8A779MD SoC.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Link: https://patch.msgid.link/20260504144534.43745-5-marek.vasut+renesas@mailbox.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>