tools: bpftool: remove unnecessary 'if' to reduce indentation

It is obvious we could use 'else if' instead of start a new 'if' in the
touched code.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>