ixgbe: cleanup namespace complaint by removing little used function

We had a support function that just walked a few pointers to get
from the ixgbe_hw struct to the netdev pointer.  This was causing
a namespace warning so I removed it and just reference the pointers
directly.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>