iwm(4), iwmfw(4): mention iwm7265Dfw

Correct documentation by mentioning iwm7265Dfw.

PR: 234584
Differential review: https://reviews.freebsd.org/D38374
Approved by: erj

(cherry picked from commit 29fa34aadbd3d93343573220a521caa0c248682d)
(cherry picked from commit 97ab40b1d7b559fa5fc3b3c18f61b38dcbca6090)