cpufreq: imx6q: Fix error handling code

According to the previous error handling code, it is likely that
'goto out_free_opp' is expected here in order to avoid a memory leak in
error handling path.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>