[S390] return address of compat signals

A 31-bit kernel always sets the high order bit in the return address
for a signal handler.
git commit d4e81b35 "[S390] allow all addressing modes" makes
sure that the high order bit is set in the signal return address for
standard signals of a 31-bit compat process but fails to do the same
for real-time signals. To make things consistent the bit needs to be
set by setup_rt_frame32 as well.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/compat_signal.c

@@ -548,9 +548,9 @@ static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
 	/* Set up to return from userspace.  If provided, use a stub
 	   already in userspace.  */
 	if (ka->sa.sa_flags & SA_RESTORER) {
-		regs->gprs[14] = (__u64) ka->sa.sa_restorer;
+		regs->gprs[14] = (__u64) ka->sa.sa_restorer | PSW32_ADDR_AMODE;
 	} else {
-		regs->gprs[14] = (__u64) frame->retcode;
+		regs->gprs[14] = (__u64) frame->retcode | PSW32_ADDR_AMODE;
 		err |= __put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn,
 				  (u16 __force __user *)(frame->retcode));
 	}