power: twl4030: 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: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/twl4030_charger.c

@@ -726,10 +726,10 @@ twl4030_bci_mode_show(struct device *dev,
 
 	for (i = 0; i < ARRAY_SIZE(modes); i++)
 		if (mode == i)
-			len += snprintf(buf+len, PAGE_SIZE-len,
+			len += scnprintf(buf+len, PAGE_SIZE-len,
 					"[%s] ", modes[i]);
 		else
-			len += snprintf(buf+len, PAGE_SIZE-len,
+			len += scnprintf(buf+len, PAGE_SIZE-len,
 					"%s ", modes[i]);
 	buf[len-1] = '\n';
 	return len;