scsi: Stop installing both cam.4 and CAM.4

There's no real benefit from installing both cam.4 and CAM.4. The latter
is not an kernel option. This hits a pathological case in mlinks: we're
trying to link to another file and the second link fails on
case-preserving, case-insensitive filesystems, like on MacOS by default.
Since we don't need both, avoid this pathological case.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D44346