qmp: access the local QemuOptsLists for drive option

Currently we have three QemuOptsList (qemu_common_drive_opts,
qemu_legacy_drive_opts, and qemu_drive_opts), only qemu_drive_opts
is added to vm_config_groups[].

This patch changes query-command-line-options to access three local
QemuOptsLists for drive option, and merge the description items
together.

Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/vl.c b/vl.c
index 4ad15b8..a585257 100644
--- a/vl.c
+++ b/vl.c
@@ -2867,6 +2867,9 @@
     module_call_init(MODULE_INIT_QOM);
 
     qemu_add_opts(&qemu_drive_opts);
+    qemu_add_drive_opts(&qemu_legacy_drive_opts);
+    qemu_add_drive_opts(&qemu_common_drive_opts);
+    qemu_add_drive_opts(&qemu_drive_opts);
     qemu_add_opts(&qemu_chardev_opts);
     qemu_add_opts(&qemu_device_opts);
     qemu_add_opts(&qemu_netdev_opts);