gpio: Get rid of gpio_hog_probe_all()

The gpio_hog_probe_all() functionality can be perfectly well replaced by
DM_FLAG_PROBE_AFTER_BIND DM flag, which would trigger .probe() callback
of each GPIO hog driver instance after .bind() and thus configure the
hogged GPIO accordingly.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>