maint: ensure src/ directory includes are clean
maint: ensure src/ directory includes are clean

In 'make syntax-check', we have a rule that prevents layering
violations between the various files in src.  However, we
forgot to treat conf/ and the more recently-added access/ as
lower-level directories, and were not detecting cases where
they might have used a driver file.  Also, it's not nice that
qemu can use storage/ but none of the other drivers could do so.

* cfg.mk (sc_prohibit_cross_inclusion): Tighten rules for conf/
and access/, let all other drivers use storage/.

Signed-off-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

datto/libvirt,nertpinx/libvirt,libvirt/libvirt,agx/libvirt,agx/libvirt,zippy2/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,agx/libvirt,fabianfreyer/libvirt,agx/libvirt,shugaoye/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt,elmarco/libvirt,taget/libvirt,olafhering/libvirt,libvirt/libvirt,andreabolognani/libvirt,nertpinx/libvirt,eskultety/libvirt,andreabolognani/libvirt,taget/libvirt,elmarco/libvirt,fabianfreyer/libvirt,rlaager/libvirt,zippy2/libvirt,datto/libvirt,jfehlig/libvirt,jardasgit/libvirt,crobinso/libvirt,elmarco/libvirt,VenkatDatta/libvirt,crobinso/libvirt,taget/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,rlaager/libvirt,shugaoye/libvirt,crobinso/libvirt,nertpinx/libvirt,nertpinx/libvirt,datto/libvirt,eskultety/libvirt,zippy2/libvirt,rlaager/libvirt,libvirt/libvirt,shugaoye/libvirt,jfehlig/libvirt,rlaager/libvirt,datto/libvirt,elmarco/libvirt,eskultety/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,zippy2/libvirt,taget/libvirt,VenkatDatta/libvirt,eskultety/libvirt,rlaager/libvirt,eskultety/libvirt,andreabolognani/libvirt,crobinso/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,datto/libvirt,elmarco/libvirt,libvirt/libvirt,agx/libvirt,andreabolognani/libvirt,taget/libvirt,nertpinx/libvirt,jardasgit/libvirt,shugaoye/libvirt,jfehlig/libvirt,shugaoye/libvirt,olafhering/libvirt