ASoC: rsnd: rsnd_mod_name() handles both name and ID

Current rsnd driver is using "%s[%d]" for mod name and ID,
but, this ID portion might confusable.
For example currently, CTU ID is 0 to 7, but using 00 to 13
(= 00, 01, 02, 03, 10, 11, 12, 13) is very best matching to datasheet.

In the future, we will support BUSIFn, but it will be more complicated
numbering. To avoid future confusable code, this patch modify
rsnd_mod_name() to return understandable name.

To avoid using pointless memory, it uses static char and snprintf,
thus, rsnd_mod_name() user should use it immediately, and shouldn't keep
its pointer.

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