bnx2x: Fix the race on bp->stats_pending.

Fix the race on bp->stats_pending between the timer and a LINK_UP event
handler.

Signed-off-by: Vladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>