MFC r332997:

Translate 32-bit ifmedia requests into native ones.

We use transformation rather than accessors as virtually ever driver
implements SIOCGIFMEDIA and all would have to be touched.

Keep the code readable by always performing copies and (possiably no-op)
transforms.

Reviewed by: jhb, kib
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14996