isofs: Verify inode mode when loading from disk

Verify that the inode mode is sane when loading it from the disk to
avoid complaints from VFS about setting up invalid inodes.

Reported-by:  <syzbot+895c23f6917da440ed0d@syzkaller.appspotmail.com>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/20250709095545.31062-2-jack@suse.cz


Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>