New QMP command query-cpu-max and HMP command cpu_max

These commands return the maximum number of CPUs supported by the
currently running emulator instance, as defined in its QEMUMachine
struct.

Signed-off-by: Michal Novotny <minovotn@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/vl.c b/vl.c
index aeed7f4..7643f16 100644
--- a/vl.c
+++ b/vl.c
@@ -662,6 +662,11 @@
     return info;
 }
 
+int64_t qmp_query_cpu_max(Error **errp)
+{
+    return current_machine->max_cpus;
+}
+
 /***********************************************************/
 /* real time host monotonic timer */