e1000e: cleanup boolean comparison to true

Removing a comparison to the boolean value true where simply interrogating
the lvalue will produce the same result.

Signed-off-by: David Ertman <davidx.m.ertman@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>