thermal: cpu_cooling: Check memory allocation of power_table

We allocate the power_table in memory but we don't test whether the
allocation succeeded.  Return -ENOMEM if kcalloc() fails.

Fixes: e0128d8ab423 ("thermal: cpu_cooling: implement the power cooling device API")
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>