iwlwifi: fix the build

Pull in a case statement from the upcoming iwlwifi update to
unbreak the build after d875aa1587ce7d1651cabe395ed991f2384795cd .

Reported by: cy
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
X-MFC with: d875aa1587ce7d1651cabe395ed991f2384795cd