fix QemuOpts leak

Now that no backend's open function saves the passed QemuOpts, fix a leak
in the qemu_chr_open backwards-compatible parser.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

qemu-char.c

@@ -2559,6 +2559,7 @@ CharDriverState *qemu_chr_open(const char *label, const char *filename, void (*i
     if (chr && qemu_opt_get_bool(opts, "mux", 0)) {
         monitor_init(chr, MONITOR_USE_READLINE);
     }
+    qemu_opts_del(opts);
     return chr;
 }