virtio gpu sparse warning

[Michael S. Tsirkin]

sparse produces these warnings:

drivers/gpu/drm/virtio/virtgpu_fb.c:340:27: warning: incorrect type in
assignment (different address spaces)
drivers/gpu/drm/virtio/virtgpu_fb.c:340:27:    expected char [noderef]
<asn:2>*screen_base
drivers/gpu/drm/virtio/virtgpu_fb.c:340:27:    got void *vmap

This is because the expected type is void __iomem *, while
virtio gpu object is void *vmap.

We could just cast the warning away but I'm not sure this
is not a symptom of an actual problem. For example, might
some code call iounmap on this address?

-- 
MST