ext4: fix build failure without procfs

fs/ext4/super.c: In function 'ext4_fill_super':
fs/ext4/super.c:2226: error: 'ext4_ui_proc_fops' undeclared (first use
in this function)
fs/ext4/super.c:2226: error: (Each undeclared identifier is reported
only once
fs/ext4/super.c:2226: error: for each function it appears in.)
Signed-off-by: NAlexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -2231,6 +2231,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount;
 	}
 
+#ifdef CONFIG_PROC_FS
 	if (ext4_proc_root)
 		sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root);
 
@@ -2238,6 +2239,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		proc_create_data("inode_readahead_blks", 0644, sbi->s_proc,
 				 &ext4_ui_proc_fops,
 				 &sbi->s_inode_readahead_blks);
+#endif
 
 	bgl_lock_init(&sbi->s_blockgroup_lock);