bnx2x: Load/Unload under traffic

Load/Unload under traffic
Few issues were found when loading and unloading under traffic:
- When receiving Tx interrupt call netif_wake_queue if the queue is
  stopped but the state is open
- Check that interrupts are enabled before doing anything else on the
  msix_fp_int function
- In nic_load, enable the interrupts only when needed and ready for it
- Function stop_leading returns status since it can fail
- Add 1ms delay when unloading the driver to validate that there are no
  open transactions that already started by the FW
- Splitting the "has work" function into Tx and Rx so the same function
  will be used on unload and interrupts
- Do not request for WoL if only resetting the device (save the time
  that it takes the FW to set the link after reset)
- Fixing the device reset after iSCSI boot and before driver load - all
  internal buffers must be cleared before the driver is loaded

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>