HMP: Use QMP inject nmi implementation

This **CHANGES** the human monitor "nmi" command behavior.

Currently it accepts an CPU argument which, when provided, will send
the NMI to the specified CPU. This feature is of discussable value
though and HMP shouldn't have more features than QMP, so let's use
QMP's instead (it's also simpler).

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 834e6a8..6ad8806 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -740,10 +740,11 @@
 #if defined(TARGET_I386)
     {
         .name       = "nmi",
-        .args_type  = "cpu_index:i",
-        .params     = "cpu",
-        .help       = "inject an NMI on the given CPU",
-        .mhandler.cmd = do_inject_nmi,
+        .args_type  = "",
+        .params     = "",
+        .help       = "inject an NMI on all guest's CPUs",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_inject_nmi,
     },
 #endif
 STEXI