bpf, xdp: backports from upstream (phase 2)

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2218483

Backporting safe upstream fixes to bpf that are missing so far.

Backporting 78fa0d61d97a ("bpf, sockmap: Pass skb ownership through
read_skb") required dependencies to be backported as well:

• 31f1fbcb346c ("udp: Refactor udp_read_skb()")
• d6e3b27cbd2d ("af_unix: Refactor unix_read_skb()")

Signed-off-by: Felix Maurer fmaurer@redhat.com