Input: pwm-beeper - suppress error message on probe defer

This suppress printing an error message when pwm_get returns -EPROBE_DEFER.
Otherwise you get a bunch of noise in the kernel log.

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>