s390: correct some inline assembly constraints

Inline assembly code changed in this patch should really use "Q"
constraint "Memory reference without index register and with short
displacement". The kernel does not compile with kasan support enabled
otherwise (due to stack instrumentation).

Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>