drm: Update deprecation message
Update the deprecation message in the drm1 (aka legacy drm or drm-legacy)
drivers to not point towards the drm-legacy-kmod port, as that is being
This is a direct commit to stable/12 since the drm1 code has been removed
from 13 already.
Reviewed by: imp
Approved by: imp
Differential Revision: https://reviews.freebsd.org/D26175