When an SCST provider is registered, it needs to know what
local ports are available for configuration as targets.

Add a notifier chain that is invoked when any local port
that is added or deleted.

Maintain a global list of local ports and add an
interator function that calls a given function for
every existing local port.  This is used when first
loading a provider.
Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>