bpf, doc: add missing patchwork url and libbpf to maintainers

Add missing bits under tools/lib/bpf/ and also Q: entry in order to
make it easier for people to retrieve current patch queue.
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>

MAINTAINERS

@@ -2722,6 +2722,7 @@ L:	netdev@vger.kernel.org
 L:	linux-kernel@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git
+Q:	https://patchwork.ozlabs.org/project/netdev/list/?delegate=77147
 S:	Supported
 F:	arch/x86/net/bpf_jit*
 F:	Documentation/networking/filter.txt
@@ -2740,6 +2741,7 @@ F:	net/sched/act_bpf.c
 F:	net/sched/cls_bpf.c
 F:	samples/bpf/
 F:	tools/bpf/
+F:	tools/lib/bpf/
 F:	tools/testing/selftests/bpf/
 
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