PM / devfreq: event: Remove the error log of devfreq_event_get_edev_by_phandle()

This patch just removes the error log when
devfreq_event_get_edev_by_phandle() fail to get the instance of
devfreq-event device. It is related to sequence of the probe() of each
driver. So, this error log might show the always during kernel booting.
Each driver using this function can show the appropriate error log.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>