qerror: Improve QERR_DEVICE_NOT_ACTIVE message

The error message as currently used is confusing as there are no "balloon" or
"spice" devices.

(qemu) balloon 1024
balloon: Device 'balloon' has not been activated

With this patch:

(qemu) balloon 1024
balloon: No balloon device has been activated
Signed-off-by: NHani Benhabiles <hani@linux.com>
Suggested-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

include/qapi/qmp/qerror.h

@@ -105,7 +105,7 @@ void qerror_report_err(Error *err);
     ERROR_CLASS_GENERIC_ERROR, "Device '%s' does not support hotplugging"
 
 #define QERR_DEVICE_NOT_ACTIVE \
-    ERROR_CLASS_DEVICE_NOT_ACTIVE, "Device '%s' has not been activated"
+    ERROR_CLASS_DEVICE_NOT_ACTIVE, "No %s device has been activated"
 
 #define QERR_DEVICE_NOT_ENCRYPTED \
     ERROR_CLASS_GENERIC_ERROR, "Device '%s' is not encrypted"