selftests: psock_tpacket: fix status check

Testing like this for TP_STATUS_AVAILABLE clearly is a stupid bug
since it always returns true. Fix this by only checking for flags
where the kernel owns the packet and negate this result, since we
also could run into the non-zero status TP_STATUS_WRONG_FORMAT
and need to reclaim frames.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>