DynamicTablesPkg/AmlLib: Fix refactor AmlCodeGenInvokeMethod API

CLANG CI shows that ArgCountNode can be used uninitialized. This is
a genuine error, it should be NULL-ed before any `goto exit_handler`.

Fixes: 1774a34

Signed-off-by: Mike Beaton <[email protected]>

Author: mikebeaton

DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlCodeGen.c

@@ -4028,6 +4028,7 @@ AmlCodeGenInvokeMethod (
   }
 
   MethodInvocationNode = NULL;
+  ArgCountNode         = NULL;
 
   NodeStream = AllocateZeroPool (sizeof (AML_NODE_HANDLE) * (NumArgs + 1));
   if (NodeStream == NULL) {
@@ -4167,13 +4168,12 @@ AmlCodeGenInvokeMethod (
     goto exit_handler;
   }
 
-  ArgCountNode = NULL;
-  Status       = AmlCreateDataNode (
-                   EAmlNodeDataTypeUInt,
-                   &NumArgs,
-                   sizeof (UINT8),
-                   &ArgCountNode
-                   );
+  Status = AmlCreateDataNode (
+             EAmlNodeDataTypeUInt,
+             &NumArgs,
+             sizeof (UINT8),
+             &ArgCountNode
+             );
   if (EFI_ERROR (Status)) {
     ASSERT_EFI_ERROR (Status);
     goto exit_handler;