gpio: Propagate all errors in devm_get_gpiod_from_child()

devm_get_gpiod_from_child() tries several property suffixes to find a
GPIO descriptor. If all suffixes fail and no probe deferral has been
detected, it returns the error of the last try.

However, if any but the last try fails with a real error (e.g. -EBUSY),
this error is not propagated, and -ENOENT will be returned.
This confuses drivers that e.g. want to detect if a GPIO is already in
use.

To fix this, change the loop logic to continue on -ENOENT, which
indicates the property was not found and the next suffix should be
tried, and propagate all other detected errors.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>