Revert "bpf, sockmap: Pass skb ownership through read_skb"

This reverts commit 4ae2af3e.

It breaks the Android KABI and will be brought back at a later time when
it is safe to do so.

Bug: 161946584
Change-Id: I86bb2f6a68328744a796648dd8ec907580dd2c0b
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>