HID: hid-picolcd_fb: 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>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-picolcd_fb.c

@@ -459,9 +459,9 @@ static ssize_t picolcd_fb_update_rate_show(struct device *dev,
 		if (ret >= PAGE_SIZE)
 			break;
 		else if (i == fb_update_rate)
-			ret += snprintf(buf+ret, PAGE_SIZE-ret, "[%u] ", i);
+			ret += scnprintf(buf+ret, PAGE_SIZE-ret, "[%u] ", i);
 		else
-			ret += snprintf(buf+ret, PAGE_SIZE-ret, "%u ", i);
+			ret += scnprintf(buf+ret, PAGE_SIZE-ret, "%u ", i);
 	if (ret > 0)
 		buf[min(ret, (size_t)PAGE_SIZE)-1] = '\n';
 	return ret;