ext4: move sysfs code from super.c to fs/ext4/sysfs.c

Also statically allocate the ext4_kset and ext4_feat objects, since we
only need exactly one of each, and it's simpler and less code if we
drop the dynamic allocation and deallocation when it's not needed.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index fd1f28b..76daccf 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2903,6 +2903,11 @@
 extern const struct inode_operations ext4_symlink_inode_operations;
 extern const struct inode_operations ext4_fast_symlink_inode_operations;
 
+/* sysfs.c */
+extern int ext4_register_sysfs(struct super_block *sb);
+extern int __init ext4_init_sysfs(void);
+extern void ext4_exit_sysfs(void);
+
 /* block_validity */
 extern void ext4_release_system_zone(struct super_block *sb);
 extern int ext4_setup_system_zone(struct super_block *sb);