fs/adfs: inode: fix adfs_mode2atts()

Fix adfs_mode2atts() to actually update the file permissions on the
media rather than using the current inode mode.  Note also that
directories do not have read/write permissions stored on the media.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>