[CIFS] BKL-removal: convert CIFS over to unlocked_ioctl

cifs_ioctl doesn't seem to need the BKL for anything, so convert it over
to use unlocked_ioctl.

Signed-off-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>