security_selinux: Replace SELinuxSCSICallbackData with proper struct

security_selinux: Replace SELinuxSCSICallbackData with proper struct

We have plenty of callbacks in the driver. Some of these
callbacks require more than one argument to be passed. For that
we currently have a data type (struct) per each callback. Well,
so far for only one - SELinuxSCSICallbackData. But lets turn it
into more general name so it can be reused in other callbacks too
instead of each one introducing a new, duplicate data type.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
(cherry picked from commit 276c409163fb94b0c325900d6e2581eaa3e3ada6)