thermal: core: use kzalloc(sizeof(*ptr),...)

thermal: core: use kzalloc(sizeof(*ptr),...)

As a safety check, this patch changes thermal
core to check for pointer content size, instead of type size,
while allocating memory.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>