revert "squashfs: harden sanity check in squashfs_read_xattr_id_table"

This fix was nacked by Philip, for reasons identified in the email linked
below.

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: 72e544b1b28325 ("squashfs: harden sanity check in squashfs_read_xattr_id_table")
Cc: Alexey Khoroshilov <[e-mail]>
Cc: Fedor Pchelkin <[e-mail]>
Cc: Phillip Lougher <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/squashfs/xattr_id.c

···
 	/* Sanity check values */
 
 	/* there is always at least one xattr id */
-	if (*xattr_ids <= 0)
+	if (*xattr_ids == 0)
 		return ERR_PTR(-EINVAL);
 
 	len = SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids);