ext2: add warning when specifying nocheck option

The option nocheck(nocheck/check=none) is useless but considering
backwards compatibility it's better to print warning for a while
before completely remove from the code.

This patch add proper warning message for option 'nocheck' and
remove unnecessary comment/function declaration which is used for
removed option 'check'.

Signed-off-by: Chengguang Xu <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ext2/ext2.h

···
 			      unsigned long);
 extern unsigned long ext2_count_free_blocks (struct super_block *);
 extern unsigned long ext2_count_dirs (struct super_block *);
-extern void ext2_check_blocks_bitmap (struct super_block *);
 extern struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
 						    unsigned int block_group,
 						    struct buffer_head ** bh);
···
 extern struct inode * ext2_new_inode (struct inode *, umode_t, const struct qstr *);
 extern void ext2_free_inode (struct inode *);
 extern unsigned long ext2_count_free_inodes (struct super_block *);
-extern void ext2_check_inodes_bitmap (struct super_block *);
 extern unsigned long ext2_count_free (struct buffer_head *, unsigned);
 
 /* inode.c */

fs/ext2/super.c

···
 			set_opt (opts->s_mount_opt, NO_UID32);
 			break;
 		case Opt_nocheck:
+			ext2_msg(sb, KERN_WARNING,
+				"Option nocheck/check=none is deprecated and"
+				" will be removed in June 2020.");
 			clear_opt (opts->s_mount_opt, CHECK);
 			break;
 		case Opt_debug:
···
 	new_opts.s_resgid = sbi->s_resgid;
 	spin_unlock(&sbi->s_lock);
 
-	/*
-	 * Allow the "check" option to be passed as a remount option.
-	 */
 	if (!parse_options(data, sb, &new_opts))
 		return -EINVAL;