vmwgfx: minor dmabuf utilities cleanup

Add / fix some function comments.
Don't move out an fbdev framebuffer when unused. Just unpin.
Only have a single function that computes a SVGAGuestPtr from the buffer's
current placement, and make it more versatile by accepting a
struct ttm_buffer_object

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c b/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
index e74b8e3..347e406 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
@@ -168,7 +168,7 @@
 	cmd->obj.root.y = y;
 
 	/* Ok to assume that buffer is pinned in vram */
-	vmw_dmabuf_get_guest_ptr(sou->buffer, &cmd->obj.backingStore.ptr);
+	vmw_bo_get_guest_ptr(&sou->buffer->base, &cmd->obj.backingStore.ptr);
 	cmd->obj.backingStore.pitch = mode->hdisplay * 4;
 
 	vmw_fifo_commit(dev_priv, fifo_size);