drm/core: clean up references to drm_dev_unref()

This is a continuation of a previous commit ("drm: introduce drm_dev_{get/put}
functions") to replace all references to drm_dev_unref() in drm core files with
drm_dev_put().

Signed-off-by: Aishwarya Pant <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/20170926170400.GA7671@aishwarya
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 782b95e..8de93a2 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -342,7 +342,7 @@ void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
 	/* drop the reference on the export fd holds */
 	drm_gem_object_put_unlocked(obj);
 
-	drm_dev_unref(dev);
+	drm_dev_put(dev);
 }
 EXPORT_SYMBOL(drm_gem_dmabuf_release);