ixgbe: fix checkpatch style of blank line after declaration

This patch fixes checkpatch warnings in ixgbe, by adding a blank line
between declaration and code blocks.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>