multifd: Make no compression operations into its own structure

It will be used later.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

---

No comp value needs to be zero.

migration/migration.c

@@ -2245,6 +2245,15 @@ int migrate_multifd_channels(void)
     return s->parameters.multifd_channels;
 }
 
+MultiFDCompression migrate_multifd_compression(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->parameters.multifd_compression;
+}
+
 int migrate_use_xbzrle(void)
 {
     MigrationState *s;