e1000e: checkpatch error - macro panethesis

ERROR: Macros with complex values should be enclosed in parenthesis

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>