bpftool: Fix compilation warning on shadowed variable

The ident variable has already been declared at the top of the function
and doesn't need to be re-declared.

Fixes: 985ead416d ("bpftool: Add skeleton codegen command")
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216112733.GA28366@Omicron

tools/bpf/bpftool/gen.c

@@ -388,7 +388,7 @@ static int do_skeleton(int argc, char **argv)
 		);
 		i = 0;
 		bpf_object__for_each_map(map, obj) {
-			const char *ident = get_map_ident(map);
+			ident = get_map_ident(map);
 
 			if (!ident)
 				continue;