bnx2x: Protect statistics ramrod and sequence number

Bug fix: Protect statistics ramrod sending code and a statistics counter update
with a spinlock. Otherwise there was a race condition that would allow sending
a statistics ramrods with the same sequence number or with sequence numbers not
in a natural order, which would cause a FW assert.

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