spice: load module when enabled on the cmdline

In case the spice opts are not registered, try loading the spice module.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20201019075224.14803-10-kraxel@redhat.com
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 8a06fe8..14fc527 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -3705,7 +3705,11 @@
                     break;
                 }
             case QEMU_OPTION_spice:
-                olist = qemu_find_opts("spice");
+                olist = qemu_find_opts_err("spice", NULL);
+                if (!olist) {
+                    ui_module_load_one("spice-core");
+                    olist = qemu_find_opts("spice");
+                }
                 if (!olist) {
                     error_report("spice support is disabled");
                     exit(1);