ASoC: soc-core.c: fixup snd_soc_of_get_dai_link_cpus()

Merge series from Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>:

Current ASoC has fixup both snd_soc_of_get_dai_link_cpus/codecs().
I guess cpu was copied from codec, but it is using "codec" naming everwhere
in "cpu" function. It is strange, and thus, error case will be issue
(It should call cpu function instead of codec).

This patch tidyup it, and try to cleanup.
[1/2] is for bug-fix,
[2/2] is for new feature.