ASoC: rsnd: SSI/SSIU use rsnd_get_slot_extend() to check TDM

Current SSI/SSIU are using rsnd_get_slot_runtime() to check TDM,
but using rsnd_get_slot_extend() is more sane.
This patch fix it up

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>