cpufreq: error path fixes

cpufreq: error path fixes

This fixes an actual bug (failure to exit from a function after an
allocation failure), an inconsistency (not removing the cpufreq_dom
list member upon failure), and a latent bug (not clearing the current
governor upon governor initialization failure when there was no old
one; latent because the only current code path leading to this
situation frees the policy upon failure and hence the governor not
getting cleared is benign).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>