drm: move drm_mmap to <drm/drm_legacy.h>

Now that we've removed the copypasted users in gem/ttm we can
relegate the legacy buffer mapping support to where it belongs.
Also give it the proper drm_legacy_ prefix.

While at it statify drm_mmap_locked, somehow I've missed that in my
previous header rework.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_legacy.h b/include/drm/drm_legacy.h
index 6486306..3e69803 100644
--- a/include/drm/drm_legacy.h
+++ b/include/drm/drm_legacy.h
@@ -157,6 +157,7 @@
 int drm_legacy_rmmap(struct drm_device *d, struct drm_local_map *map);
 int drm_legacy_rmmap_locked(struct drm_device *d, struct drm_local_map *map);
 struct drm_local_map *drm_legacy_getsarea(struct drm_device *dev);
+int drm_legacy_mmap(struct file *filp, struct vm_area_struct *vma);
 
 int drm_legacy_addbufs_agp(struct drm_device *d, struct drm_buf_desc *req);
 int drm_legacy_addbufs_pci(struct drm_device *d, struct drm_buf_desc *req);