gpio: aggregator: Return an error if there are no GPIOs in gpio_aggregator_parse()

gpio: aggregator: Return an error if there are no GPIOs in gpio_aggregator_parse()

The error handling in gpio_aggregator_parse() was re-written.  It now
returns success if there are no GPIOs.  Restore the previous behavior
and return -EINVAL instead.

Fixes: 83c8e3df642f ("gpio: aggregator: expose aggregator created via legacy sysfs to configfs")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Acked-by: Koichiro Den <koichiro.den@canonical.com>
Link: https://lore.kernel.org/r/9dcd5fda7a3819e896d9eee4156e7c46c9a64595.1744452787.git.dan.carpenter@linaro.org
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>