bnx2x: prevent race in statistics flow

The race may cause access of registers while MAC hw block is
in reset state. As a result syslog will show error messages.
We can prevent this by using state from local variable.

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>