Always null-terminate ccb_pathinq.(sim_vid|hba_vid|dev_name) (part 1)

[asomers]

Summary

The sim_vid, hba_vid, and dev_name fields of struct ccb_pathinq are
fixed-length strings. AFAICT the only place they're read is in
sbin/camcontrol/camcontrol.c, which assumes they'll be null-terminated.
However, the kernel doesn't null-terminate them. A bunch of copy-pasted code
uses strncpy to write them, and doesn't guarantee null-termination. For at
least 4 drivers (mpr, mps, ciss, and hyperv), the hba_vid field actually
overflows. You can see the result by doing "camcontrol negotiate da0 -v".

This change null-terminates those fields everywhere they're set in the
kernel. It also shortens a few strings to ensure they'll fit within the
16-character field.

[imp]

This change is largely a no-op in terms of effect.
However, it eliminates dozens of false-positive uses of strncpy which people get wrong all the time and ensure that if cam_sim_name() is super-duper long we do something sensible (or at least fail-safe better than today's missing NUL). It's also a tiny performance win, but I doubt anybody can measure the effects of saving a few dozen cycles on boot.

[asomers]

Fixed by r311305