FROMLIST: 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 <gwendal@chromium.org>
(am from https://lore.kernel.org/r/20220204062232.3410036-1-gwendal@chromium.org)

BUG=b:205899437
TEST=With the patch reverted, we can mount an image copied from
the EV3

Change-Id: I731be37a6305e4d5378ac4d31817adcbd43e9c62
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3430762
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Daniil Lunev <dlunev@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
(cherry picked from commit f67697eb16412d5a1b5a633b619e129425afcec0)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3498707

fs/fat/inode.c

@@ -495,24 +495,6 @@ 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)
 {
@@ -539,10 +521,6 @@ 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,