Update CustomOp's attribute Names

- CustomOp's two attribute names have been changed to
  - domain to domain_name
  - operator to operator_name

Signed-off-by: Jerry Ge <jerry.ge@arm.com>
Change-Id: I382ff2cf98da0487f096938c3693428e91dce386
diff --git a/include/attribute.def b/include/attribute.def
index dc7a569..8d74ff9 100644
--- a/include/attribute.def
+++ b/include/attribute.def
@@ -124,8 +124,8 @@
               int32_t, S, output_zp)
 
 DEF_ATTRIBUTE(Custom, 3,
-              string, S, identifier,
-              string, S, config,
+              string, S, operator_name,
+              string, S, domain_name,
               uint8_t, V, implementation_attrs)
 
 DEF_ATTRIBUTE(FFT, 2,
@@ -134,4 +134,3 @@
 
 DEF_ATTRIBUTE(RFFT, 1,
               bool, S, local_bound)
-