[S390] fix disabled_wait inline assembly clobber list

The disabled_wait inline assmembly also clobbers register r1, but it
is missing in the clobber list.
Fixes recursive Oops on panic.

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