LinuxKPI: 802.11: fix types and whitespace

Correct struct member types, fix whitespace, and remove superfluous
return statements in void functions.

No functional changes.

Sponsored by: The FreeBSD Foundation
Approved by: re (cperciva)

(cherry picked from commit a3baca22d0b7789a040a60f389e3c132b6e1755b)
(cherry picked from commit d282e777d7c9721614f110a1de66c7d88d0a6ea8)