dma-buf: Improve a size determination in dma_buf_attach()

Replace the specification of a data structure by a pointer dereference
as the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style convention.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

drivers/dma-buf/dma-buf.c

@@ -558,7 +558,7 @@ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 	if (WARN_ON(!dmabuf || !dev))
 		return ERR_PTR(-EINVAL);
 
-	attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
+	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
 	if (attach == NULL)
 		return ERR_PTR(-ENOMEM);