chardev: add msmouse support to qapi

This patch adds 'msmouse' support to qapi and also switches over
the msmouse chardev initialization to the new qapi code path.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/qemu-char.c b/qemu-char.c
index e6f67d8..e860ba3 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3719,6 +3719,9 @@
         }
         chr = qemu_chr_open_mux(base);
         break;
+    case CHARDEV_BACKEND_KIND_MSMOUSE:
+        chr = qemu_chr_open_msmouse();
+        break;
     default:
         error_setg(errp, "unknown chardev backend (%d)", backend->kind);
         break;