Why
Some files in DRM rely on namespace pollution: they use the <linux/rcupdate.h> API without including it explicitly.
How
Reproduce the Linux chain of includes even if it means nothing on FreeBSD. This allows consumers of <linux/idr.h> to "inherit" <linux/rcupdate.h> API.
This is part of the update of DRM drivers to Linux 6.7.
Sponsored by: The FreeBSD Foundation