[S390] addressing mode limits and psw address wrapping

An instruction with an address right below the adress limit for the
current addressing mode will wrap. The instruction restart logic in
the protection fault handler and the signal code need to follow the
wrapping rules to find the correct instruction address.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/signal.c

@@ -447,8 +447,9 @@ void do_signal(struct pt_regs *regs)
 			/* fallthrough */
 			case -ERESTARTNOINTR:
 				regs->gprs[2] = regs->orig_gpr2;
-				regs->psw.addr = regs->psw.addr -
-					(regs->svc_code >> 16);
+				regs->psw.addr =
+					__rewind_psw(regs->psw,
+						     regs->svc_code >> 16);
 				break;
 			}
 			/* No longer in a system call */