Allow passing optional gpiochip number before gpio number.
If no optional chip number is passed, the one from the 'gpiochip'
configuration directive is used.
Change-Id: I16933d81581d9af4d1600c5f9fdbc832ef3fda94
Signed-off-by: Laszlo Sitzer <dlsitzer@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6742
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>