fwcamctl: remove, superseded by the video(4) interface

fwcam(4) no longer creates its own character device or implements the
FWCAM_* ioctls; it registers with video(4) and is driven through the
standard V4L2 interface on /dev/videoN.

Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D58500