um: process: remove unused 'n' variable

The return value of fn() wasn't used for a long time,
so no need to assign it to a variable, addressing a
W=1 warning.

This seems to be - with patches from others posted to
the list before - the last W=1 warning in arch/um/.

Fixes: 22e2430d ("x86, um: convert to saner kernel_execve() semantics")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/kernel/process.c

@@ -109,7 +109,7 @@ int get_current_pid(void)
  */
 void new_thread_handler(void)
 {
-	int (*fn)(void *), n;
+	int (*fn)(void *);
 	void *arg;
 
 	if (current->thread.prev_sched != NULL)
@@ -122,7 +122,7 @@ void new_thread_handler(void)
 	/*
 	 * callback returns only if the kernel thread execs a process
 	 */
-	n = fn(arg);
+	fn(arg);
 	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
 }