ASoC: wm_adsp: Use scnprintf() for the limited buffer output

ASoC: wm_adsp: Use scnprintf() for the limited buffer output

snprintf() is a hard-to-use function, it's especially difficult to use
it for concatenating substrings in a buffer with a limited size.
Since snprintf() returns the would-be-output size, not the actual
size, the subsequent use of snprintf() may point to the incorrect
position.

Use scnprintf() instead for fixing such potential errors.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20200313130334.9028-1-tiwai@suse.de
Signed-off-by: Mark Brown <broonie@kernel.org>