Staging: VME: Make vme/ctl device available for IOCTL operations only.

Resurrect the vme/ctl device by allowing to open it even if it has no resources
and make related read/write/llseek operations dummy.

Signed-off-by: Vincent Bossier <vincent.bossier@gmail.com>
Acked-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>