qerror.h: Remove QERR defines that are only used once

Just hardcode them in the callers

Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index bf42c04..a2bed1e 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -71,7 +71,7 @@
     GHashTable *h;
 
     if (qiv->nb_stack >= QIV_STACK_SIZE) {
-        error_set(errp, QERR_BUFFER_OVERRUN);
+        error_setg(errp, "An internal buffer overran");
         return;
     }