super.c: unused variable warning without CONFIG_QUOTA

sb info is only checked with quota support.

fs/ext4/super.c: In function ‘parse_options’:
fs/ext4/super.c:1600:23: warning: unused variable ‘sbi’ [-Wunused-variable]

Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6da1935..e1fb1d5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1597,7 +1597,9 @@
 			 unsigned int *journal_ioprio,
 			 int is_remount)
 {
+#ifdef CONFIG_QUOTA
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
+#endif
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
 	int token;