bpftool: Migrate off of deprecated bpf_create_map_xattr() API

Switch to bpf_map_create() API instead.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211201232824.3166325-4-andrii@kernel.org