dt-bindings: serial: rsci: Update maintainer entry

Add myself as the maintainer for the Renesas RSCI device tree binding,
as Thierry Bultel no longer works for Renesas.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://lore.kernel.org/r/20250630202323.279809-3-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: prabhakarlad

Documentation/devicetree/bindings/serial/renesas,rsci.yaml

@@ -8,7 +8,7 @@ title: Renesas RSCI Serial Communication Interface
 
 maintainers:
   - Geert Uytterhoeven <geert+renesas@glider.be>
-  - Thierry Bultel <thierry.bultel.yh@bp.renesas.com>
+  - Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
 
 allOf:
   - $ref: serial.yaml#