usb: gadget: FunctionFS: Use kstrtoul()

kstrtoul() checks for overflow which simple_strtoul() does not pluss
it has “*end == 0” check in it as well.  As a side effect, a new
line character is now accepted, but this should not be an issue.
Signed-off-by: NMichal Nazarewicz <mina86@mina86.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_fs.c

@@ -1103,8 +1103,8 @@ static int ffs_fs_parse_opts(struct ffs_sb_fill_data *data, char *opts)
 		return 0;
 
 	for (;;) {
-		char *end, *eq, *comma;
 		unsigned long value;
+		char *eq, *comma;
 
 		/* Option limit */
 		comma = strchr(opts, ',');
@@ -1120,8 +1120,7 @@ static int ffs_fs_parse_opts(struct ffs_sb_fill_data *data, char *opts)
 		*eq = 0;
 
 		/* Parse value */
-		value = simple_strtoul(eq + 1, &end, 0);
-		if (unlikely(*end != ',' && *end != 0)) {
+		if (kstrtoul(eq + 1, 0, &value)) {
 			pr_err("%s: invalid value: %s\n", opts, eq + 1);
 			return -EINVAL;
 		}