um: remove dead code

"me" is not used.

Signed-off-by: Richard Weinberger <richard@nod.at>

arch/x86/um/signal.c

@@ -508,7 +508,6 @@ int setup_signal_stack_si(unsigned long stack_top, int sig,
 {
 	struct rt_sigframe __user *frame;
 	int err = 0;
-	struct task_struct *me = current;
 
 	frame = (struct rt_sigframe __user *)
 		round_down(stack_top - sizeof(struct rt_sigframe), 16);