bnx2x: Statistics

Statistics
- Making sure that each drop is accounted for in the driver statistics
- Clearing the FW statistics when driver is loaded to prevent
  inconsistency with HW statistics
- Once error is detected (bnx2x_panic_dump), stop the statistics
  before other actions (currently it is stopped last and can corrupt
  the data) - Adding HW checksum error counter to the statistics
- Removing unused variable stats_ticks
- Using macros instead of magic numbers to indicate which statistics are
  shared per port and which are per function

Signed-off-by: Yitchak Gertner <gertner@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>