e1000e: rename e1000e_reload_nvm() and call as function pointer

Rename e1000e_reload_nvm() to e1000e_reload_nvm_generic() to signify the
function is used for more than one MAC-family type, and set and use it as a
MAC ops function pointer to be consistent with the driver design.

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>