ext4: Remove unused extern variables declaration

ext4_mb_stats & ext4_mb_max_to_scan are never used. We use
sbi->s_mb_stats and sbi->s_mb_max_to_scan instead.
Hence kill these extern declarations.
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/928b3142062172533b6d1b5a94de94700590fef3.1685449706.git.ojaswin@linux.ibm.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -2837,8 +2837,6 @@ int ext4_fc_record_regions(struct super_block *sb, int ino,
 /* mballoc.c */
 extern const struct seq_operations ext4_mb_seq_groups_ops;
 extern const struct seq_operations ext4_mb_seq_structs_summary_ops;
-extern long ext4_mb_stats;
-extern long ext4_mb_max_to_scan;
 extern int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset);
 extern int ext4_mb_init(struct super_block *);
 extern int ext4_mb_release(struct super_block *);

fs/ext4/mballoc.h

@@ -49,7 +49,7 @@
 #define MB_DEFAULT_MIN_TO_SCAN		10
 
 /*
- * with 'ext4_mb_stats' allocator will collect stats that will be
+ * with 's_mb_stats' allocator will collect stats that will be
  * shown at umount. The collecting costs though!
  */
 #define MB_DEFAULT_STATS		0