Fix kernel/ptrace.c compile problem (missing "may_attach()")

The previous commit missed one use of "may_attach()" that had been
renamed to __ptrace_may_attach().  Tssk, tssk, Al.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/ptrace.c

@@ -196,7 +196,7 @@ int ptrace_attach(struct task_struct *task)
 	/* the same process cannot be attached many times */
 	if (task->ptrace & PT_PTRACED)
 		goto bad;
-	retval = may_attach(task);
+	retval = __ptrace_may_attach(task);
 	if (retval)
 		goto bad;