drm/msm: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/adreno_gpu.c

@@ -673,7 +673,7 @@ static char *adreno_gpu_ascii85_encode(u32 *src, size_t len)
 		return NULL;
 
 	for (i = 0; i < l; i++)
-		buf_itr += snprintf(buf + buf_itr, buffer_size - buf_itr, "%s",
+		buf_itr += scnprintf(buf + buf_itr, buffer_size - buf_itr, "%s",
 				ascii85_encode(src[i], out));
 
 	return buf;