meson: Correct driver declaration for meson_axg_gpio

This should use the driver macros so that the driver appears in the
linker list. Fix this.

Fixes: 8587839f ("pinctrl: meson: add axg support")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240623203033.1566505-8-sjg@chromium.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>