dt-bindings: gnss: u-blox: add "reset-gpios" binding

The Renesas KingFisher board includes a U-Blox Neo-M8 chip. This chip
has a reset pin which is also wired on the board. Introduce a binding to
support this reset pin.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Johan Hovold <johan@kernel.org>