PM / devfreq: rk3399_dmc: Disable devfreq-event device when fails

The probe process may fail, but the devfreq event device remains
enabled. Call devfreq_event_disable_edev on the error return path.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>