ASoC: SOF: debug: Fix potential buffer overflow by snprintf()

ASoC: SOF: debug: Fix potential buffer overflow by snprintf()

snprintf() returns the would-be-filled size when the string overflows
the given buffer size, hence using this value may result in the buffer
overflow (although it's unrealistic).

This patch replaces with a safer version, scnprintf() for papering
over such a potential issue.

Fixes: 5b10b6298921 ("ASoC: SOF: Add `memory_info` file to debugfs")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20220801165420.25978-3-tiwai@suse.de
Signed-off-by: Mark Brown <broonie@kernel.org>