drm/exynos: free sg object if dma_map_sg is failed

This patch releases sgt's sg object allocated by sgt_alloc_table
correctly.

When exynos_gem_map_dma_buf was called by dma_buf_map_attachmemt(),
the sgt's sg object was allocated by sg_alloc_tale() so
if dma_map_sg() is failed, the sg object should be released.
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_dmabuf.c

@@ -110,6 +110,7 @@ static struct sg_table *
 	nents = dma_map_sg(attach->dev, sgt->sgl, sgt->orig_nents, dir);
 	if (!nents) {
 		DRM_ERROR("failed to map sgl with iommu.\n");
+		sg_free_table(sgt);
 		sgt = ERR_PTR(-EIO);
 		goto err_unlock;
 	}