Constify unmodifiable structs, for consistency.
Reviewed-by: NChanwoo Choi <cw00.choi@samsung.com>
Tested-by: NPeter Geis <pgwipeout@gmail.com>
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Signed-off-by: NChanwoo Choi <cw00.choi@samsung.com>