fwdv: add AV/C DV capture driver for FireWire camcorders

[seuros]

Summary

Add fwdv(4) driver for DV video capture from FireWire camcorders
using AV/C protocol and isochronous streaming.

Supports AV/C tape transport commands (play, stop, ff, rewind, pause,
record, eject) with NTSC/PAL auto-detection and read(2) interface
for frame capture.

Test Plan

This requires a camcorder, not a webcam. Panasonic, Sony, Canon, JVC DV
camcorders with a 6-pin DV or full S400 FireWire port. Tested with a
Panasonic AG-HPX171 and others.

[seuros]

The Datasheet reference are marked in the driver. No new revision will ever be made, so it safe to hardcode the section.

Once this land, i will rework all the drivers to mirror USB behavior (the dev/ show up only if a device is connected).

Firewire device currently support 1 device per driver (This was here, before fwcam)