ixgbe: Add FW detection and warning for 82599 SFP+ adapters

82599 has a FW running that helps manage the internal SFI PHY.  There are
also a number of pre-production samples of these SFI-based devices in the
field.  This patch adds a check to look for the firmware running on all
SFP+ based adapters, and displays a warning to the system log if a
pre-production adapter is identified.  The driver will continue loading
though, with no functional degradation.

Also remove an old function prototype from ixgbe_82599.c that isn't being
used.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>