thermal: cpu_cooling: free power table on error or when unregistering

The power table is not being freed on error from cpufreq_cooling
register or when unregistering.  Free it.

Fixes: c36cf071 ("thermal: cpu_cooling: implement the power cooling device API")
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>