Revert "bpf, sockmap: Reschedule is now done through backlog"

This reverts commit d908a8a3 which is
commit bce22552 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id343aa8b32d977aae7bcaaa5ded89c2b895baf41
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>