cpufreq: Fix kobject memleak

Currently the error return path from kobject_init_and_add() is not
followed by a call to kobject_put() - which means we are leaking the
kobject.

Fix it by adding a call to kobject_put() in the error path of
kobject_init_and_add().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Tobin C. Harding <tobin@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>