net: aquantia: fix var initialization warning

found by sparse, simply useless local initialization with zero.

Fixes: 94ad94558b ("net: aquantia: add PTP rings infrastructure")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_ptp.c

@@ -947,7 +947,7 @@ int aq_ptp_ring_alloc(struct aq_nic_s *aq_nic)
 {
 	struct aq_ptp_s *aq_ptp = aq_nic->aq_ptp;
 	unsigned int tx_ring_idx, rx_ring_idx;
-	struct aq_ring_s *hwts = 0;
+	struct aq_ring_s *hwts;
 	u32 tx_tc_mode, rx_tc_mode;
 	struct aq_ring_s *ring;
 	int err;