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: 985ead41

 ("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