Handle files opened with flags 3 by checking ioctl permission.

Default to returning FILE__IOCTL from file_to_av() if the f_mode has neither
FMODE_READ nor FMODE_WRITE, and thus check ioctl permission on exec or
transfer, thereby validating such descriptors early as with normal r/w
descriptors and catching leaks of them prior to attempted usage.
Signed-off-by: NStephen Smalley <sds@tycho.nsa.gov>
Acked-by: NEric Paris <eparis@redhat.com>
Signed-off-by: NJames Morris <jmorris@namei.org>