opp: Free static OPPs on errors while adding them

The static OPPs aren't getting freed properly, if errors occur while
adding them. Fix that by calling _put_opp_list_kref() and putting their
reference on failures.

Fixes: 11e1a164

 ("opp: Don't decrement uninitialized list_kref")
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>