hmp: free sev info

Found thanks to ASAN:

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x7efe20417a38 in __interceptor_calloc (/lib64/libasan.so.4+0xdea38)
    #1 0x7efe1f7b2f75 in g_malloc0 ../glib/gmem.c:124
    #2 0x7efe1f7b3249 in g_malloc0_n ../glib/gmem.c:355
    #3 0x558272879162 in sev_get_info /home/elmarco/src/qemu/target/i386/sev.c:414
    #4 0x55827285113b in hmp_info_sev /home/elmarco/src/qemu/target/i386/monitor.c:684
    #5 0x5582724043b8 in handle_hmp_command /home/elmarco/src/qemu/monitor.c:3333

Fixes: 6303631
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180319175823.22111-1-marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

target/i386/monitor.c

@@ -696,6 +696,8 @@ void hmp_info_sev(Monitor *mon, const QDict *qdict)
     } else {
         monitor_printf(mon, "SEV is not enabled\n");
     }
+
+    qapi_free_SevInfo(info);
 }
 
 SevLaunchMeasureInfo *qmp_query_sev_launch_measure(Error **errp)