gnss: ubx: add support for the reset gpio

The Renesas KingFisher board includes a U-Blox Neo-M8 chip. This chip
has a reset pin which is also wired on the board. When Linux starts,
reset is asserted by the firmware. Deassert the reset pin when probing
this driver.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
[ johan: rename gpio descriptor variable ]
Signed-off-by: Johan Hovold <johan@kernel.org>