balloon: Eliminate silly QERR_ macros

The QERR_ macros are leftovers from the days of "rich" error objects.
They're used with error_set() and qerror_report(), and expand into the
first *two* arguments.  This trickiness has become pointless.  Clean
up the balloon ones.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

balloon.c

@@ -39,11 +39,13 @@ static void *balloon_opaque;
 static bool have_ballon(Error **errp)
 {
     if (kvm_enabled() && !kvm_has_sync_mmu()) {
-        error_set(errp, QERR_KVM_MISSING_CAP, "synchronous MMU", "balloon");
+        error_set(errp, ERROR_CLASS_KVM_MISSING_CAP,
+                  "Using KVM without synchronous MMU, balloon unavailable");
         return false;
     }
     if (!balloon_event_fn) {
-        error_set(errp, QERR_DEVICE_NOT_ACTIVE, "balloon");
+        error_set(errp, ERROR_CLASS_DEVICE_NOT_ACTIVE,
+                  "No balloon device has been activated");
         return false;
     }
     return true;

include/qapi/qmp/qerror.h

@@ -70,9 +70,6 @@ void qerror_report_err(Error *err);
 #define QERR_DEVICE_NO_HOTPLUG \
     ERROR_CLASS_GENERIC_ERROR, "Device '%s' does not support hotplugging"
 
-#define QERR_DEVICE_NOT_ACTIVE \
-    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"
 
@@ -109,9 +106,6 @@ void qerror_report_err(Error *err);
 #define QERR_JSON_PARSING \
     ERROR_CLASS_GENERIC_ERROR, "Invalid JSON syntax"
 
-#define QERR_KVM_MISSING_CAP \
-    ERROR_CLASS_KVM_MISSING_CAP, "Using KVM without %s, %s unavailable"
-
 #define QERR_MIGRATION_ACTIVE \
     ERROR_CLASS_GENERIC_ERROR, "There's a migration process in progress"