bnx2x: fix bnx2x_storm_stats_update() on big endian

commit 619c5cb6885 (New 7.0 FW: bnx2x, cnic, bnx2i, bnx2fc) added new
sparse warnings.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Vladislav Zolotarov <vladz@broadcom.com>
Cc: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>