e1000e: potential incorrect return for e1000_setup_copper_link_80003es2lan

In the unlikely event that e1000e_setup_copper_link() returns an error,
the returned error code value is not propogated to the caller of
e1000_setup_copper_link_80003es2lan().

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>