Documentation: gpio: fix function links in the HTML docs

The shorthand [_data] and [devm_] cause the HTML documentation to not
link to the function documentation properly. This expands the references
to the complete function names with the exception of
devm_gpiochip_remove() which was dropped by commit 48207d75 ("gpio:
drop devm_gpiochip_remove()").

Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>