Add missing section to .Xr macro calls for wpifw(4)

The driver manpage for wpifw(4) is missing, but will be added soon. This
fixes the other 2 .Xr calls lacking sections to match the 3rd,
syntactically correct, reference in the SEE ALSO section.

MFC after: 1 week
Reported by: make manlint
Sponsored by: Dell EMC Isilon