bnx2: Try to recover from PCI block reset

If the PCI block has reset, the memory enable bit will be reset and
the device will not respond to MMIO access.  bnx2_reset_task() currently
will not recover when this happens.  Add code to detect this condition
and restore the PCI state.  This scenario has been reported by some
users.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>