Merge branch 'Deprecate bpf_prog_load_xattr() API'

Andrii Nakryiko says:

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Few lines in the last patch to mark bpf_prog_load_xattr() deprecated required
a decent amount of clean ups in all the other patches. samples/bpf is big part
of the clean up.

This patch set also bumps libbpf version to 0.7, as libbpf v0.6 release will
be cut shortly.
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>