alpha: fix syscall entry in !AUDUT_SYSCALL case

We only want to take the slow path if SYSCALL_TRACE or SYSCALL_AUDIT is
set; on !AUDIT_SYSCALL configs the current tree hits it whenever _any_
thread flag (including NEED_RESCHED, NOTIFY_SIGNAL, etc.) happens to
be set.

Fixes: a9302e8439 "alpha: Enable system-call auditing support"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/alpha/kernel/entry.S

@@ -469,8 +469,10 @@ entSys:
 #ifdef CONFIG_AUDITSYSCALL
 	lda     $6, _TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT
 	and     $3, $6, $3
-#endif
 	bne     $3, strace
+#else
+	blbs    $3, strace		/* check for SYSCALL_TRACE in disguise */
+#endif
 	beq	$4, 1f
 	ldq	$27, 0($5)
 1:	jsr	$26, ($27), sys_ni_syscall