ixgbe: Cleanup the use of tabs and spaces

Cleans up the whitespace issues noticed during code review where
a mix of tabs and spaces were used for indentation.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>