e1000e: cleanup: do not assign a variable a value when not necessary

Static analysis with cppcheck has shown a few instances of a variable
being reassigned a value before the old one has been used.  None of these
ever require the old value to be used so remove the old values.

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>