ASoC: rsnd: fixup wrong snd_soc_dai_driver pointer access

drv pointer should be "base + offset" instead of
"current + offset". This patch fixup this issue, otherwise
third and subsequent pointer will be broken

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