[S390] hibernation: merge files and move to kernel/

Merge the nearly empty C files and move everything from power/ to
kernel/. That way the files are easier to handle.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>