drm: remove dev->vma_count

This is just used for a debugfs file, and we can easily reconstruct
this number by just walking the list twice. Which isn't really bad for
a debugfs file anyway.

So let's rip this out.

There's the other issue that the dev->vmalist itself is a bit useless,
since that can be reconstructed with all the memory mapping
information from proc. But remove that is a different topic entirely.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --cc drivers/gpu/drm/drm_fops.c
Simple merge

diff --cc drivers/gpu/drm/drm_info.c
Simple merge

diff --cc drivers/gpu/drm/drm_vm.c
Simple merge

diff --cc include/drm/drmP.h
Simple merge