Added missing release callback for file_operations mptctl_fops.
Without release callback there will be never freed. It remains on
mptctl's eent list even after the file is closed and released.

Relavent RHEL bugzilla is 660871

Cc: stable@kernel.org
Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>