drivers/bcm2835gpio: Migrate to adapter gpio commands

drivers/bcm2835gpio: Migrate to adapter gpio commands

Use the new "adapter gpio" commands to configure the GPIOs used by the
bcm2835gpio driver. The driver supports only 1 chip (gpiochip0).

The reset function now honours the srst_open_drain and trst_open_drain
options.

Signed-off-by: Steve Marple <stevemarple@googlemail.com>
Change-Id: I5b6c68b16362000cf5141a83394549d2bf3af108
Reviewed-on: https://review.openocd.org/c/openocd/+/7123
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>