af-packet: fix problem introduced in recent commit

Logic of patch 98e4a14f6d was correct
but implementation is wrong because TP_STATUS_KERNEL is equal to
zero and thus can not be evaluated in a binary operation. This patch
updates the logic by doing two tests.

Reported-by: Alessandro Guido

src/source-af-packet.c

@@ -723,7 +723,7 @@ int AFPReadFromRing(AFPThreadVars *ptv)
             SCReturnInt(AFP_FAILURE);
         }
 
-        if (h.h2->tp_status & (TP_STATUS_KERNEL|TP_STATUS_USER_BUSY)) {
+        if ((! h.h2->tp_status) || (h.h2->tp_status & TP_STATUS_USER_BUSY)) {
             if (read_pkts == 0) {
                 if (loop_start == -1) {
                     loop_start = ptv->frame_offset;