net: dsa: felix: initialize "err" to 0 in felix_check_xtr_pkt()

Automated tools complain that felix_check_xtr_pkt() has logic to drain
the CPU queue on the reception of a PTP packet over Ethernet, yet it
returns an uninitialized error code in the case where the CPU queue was
empty.

This is not likely to happen (/possible if hardware works correctly),
but it isn't a fatal condition either. The PTP packet will be dequeued
from the CPU queue when the next PTP packet arrives. So initialize "err"
to 0 for the case where nothing was dequeued during this iteration.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/ocelot/felix.c

@@ -1469,7 +1469,7 @@ static int felix_hwtstamp_set(struct dsa_switch *ds, int port,
 static bool felix_check_xtr_pkt(struct ocelot *ocelot)
 {
 	struct felix *felix = ocelot_to_felix(ocelot);
-	int err, grp = 0;
+	int err = 0, grp = 0;
 
 	if (felix->tag_proto != DSA_TAG_PROTO_OCELOT_8021Q)
 		return false;