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>

Update the binding file for gpio, it is just an alignment
with kernel v5.3.
The U-Boot code example for gpio-hog (not directly linked
to binding) is moved in a new file doc/README.gpio.
[commit 21676b706e99 ("gpio: fixes for gpio-hog support")
& 'commit 4762a9988ede ("gpio: add gpio-hog support")']

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>