gpio: don't warn about removing GPIO chips with active users anymore

With SRCU we can now correctly handle the situation when a GPIO provider
is removed while having users still holding references to GPIO
descriptors. Remove all warnings emitted in this situation.

Suggested-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Herve Codina <herve.codina@bootlin.com>