drm: Move drm_vm_open_locked into drm_internal.h

Leftover from my previous header cleanup.

This depends upon the patch to rework exynos mmap support, otherwise
it'll break exynos.

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/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index d27faae4..0562456 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -37,6 +37,7 @@
 
 /* drm_vm.c */
 int drm_vma_info(struct seq_file *m, void *data);
+void drm_vm_open_locked(struct drm_device *dev, struct vm_area_struct *vma);
 void drm_vm_close_locked(struct drm_device *dev, struct vm_area_struct *vma);
 
 /* drm_prime.c */