leds: pwm: silently error out on EPROBE_DEFER

When probing, if we fail to get the pwm due to probe deferal, we shouldn't
print an error message. Just be silent in this case.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>