ASoC: sh: rz-ssi: Fix dereference of noderef expression warning

Fix following sparse warning:
sound/soc/sh/rz-ssi.c:156:15: sparse: warning: dereference of
noderef expression

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20210816132049.28128-1-biju.das.jz@bp.renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>