fix double words in comments
feedback and ok jmc@ miod, ok millert@

diviedr -> divider

spelling
feedback and ok tb@ jmc@ ok ratchov@

more e-mail -> email

Spell `unused' correctly.

Driver for MosChip Semiconductor 78x0 USB multiport serial adapters.

Ported from FreeBSD via NetBSD, tested on a ST Lab U-400 provided by
weerd@.

ok jsg@