Revert "fat: add simple validation for directory inode"

This reverts commit a3082d5.

The reverted commit adds check for FAT images. However, the tools used
for creating images for the Lego Mindstrom EV3 are not adding '.' and
'..' entry in the 'Projects' directory.
Without this fix, the kernel can not fill the inode structure for
'Projects' directory.

See microsoft/pxt-ev3#980
And microsoft/uf2-linux#6

With the patch reverted, we can mount an image copied from the EV3

Signed-off-by: Gwendal Grignou <[email protected]>

fs/fat/inode.c

@@ -494,24 +494,6 @@ static int fat_calc_dir_size(struct inode *inode)
 	return 0;
 }
 
-static int fat_validate_dir(struct inode *dir)
-{
-	struct super_block *sb = dir->i_sb;
-
-	if (dir->i_nlink < 2) {
-		/* Directory should have "."/".." entries at least. */
-		fat_fs_error(sb, "corrupted directory (invalid entries)");
-		return -EIO;
-	}
-	if (MSDOS_I(dir)->i_start == 0 ||
-	    MSDOS_I(dir)->i_start == MSDOS_SB(sb)->root_cluster) {
-		/* Directory should point valid cluster. */
-		fat_fs_error(sb, "corrupted directory (invalid i_start)");
-		return -EIO;
-	}
-	return 0;
-}
-
 /* doesn't deal with root inode */
 int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
 {
@@ -538,10 +520,6 @@ int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
 		MSDOS_I(inode)->mmu_private = inode->i_size;
 
 		set_nlink(inode, fat_subdirs(inode));
-
-		error = fat_validate_dir(inode);
-		if (error < 0)
-			return error;
 	} else { /* not a directory */
 		inode->i_generation |= 1;
 		inode->i_mode = fat_make_mode(sbi, de->attr,