Revert "bpf, sockmap: Improved check for empty queue"

This reverts commit ab5b5e32 which is
commit 405df89d 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: I698905c03692a7c4da9af814c156f6f057e1df0d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>