hw/nmi: Fix the NMI() macro, based on INTERFACE_CHECK()

There is no declaration of the 'NMI' type. INTERFACE_CHECK()
returns an abstract type (see commit aa1b35b975d8). The abstract
type corresponding to the TYPE_NMI interface is 'NMIState'.

Fixes: 9cb805fd267
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20191207094823.20707-1-philmd@redhat.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

include/hw/nmi.h

@@ -31,7 +31,7 @@
 #define NMI_GET_CLASS(obj) \
     OBJECT_GET_CLASS(NMIClass, (obj), TYPE_NMI)
 #define NMI(obj) \
-     INTERFACE_CHECK(NMI, (obj), TYPE_NMI)
+     INTERFACE_CHECK(NMIState, (obj), TYPE_NMI)
 
 typedef struct NMIState NMIState;