vl: move various initialization routines out of qemu_init

Some very simple initialization routines can be nested in existing
subsystem-level functions, do that to simplify qemu_init.

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/migration/migration.c b/migration/migration.c
index 87a9b59..d9e94f4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -182,6 +182,10 @@
         error_report_err(err);
         exit(1);
     }
+
+    blk_mig_init();
+    ram_mig_init();
+    dirty_bitmap_mig_init();
 }
 
 void migration_shutdown(void)