e1000e: cleanup NAPI routine

Rename NAPI polling routine and a parameter with more appropriate names,
refactor a conditional branch to get rid of an unnecessary goto/label and
fix a line exceeding 80 columns.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>