initial support for Mega65 extra ROM

c64/kernal/iec/iec_tx_command_finalize.s

@@ -1,3 +1,5 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
+
 
 // Routine to finalize some IEC commands - which do not end in turnaround and are not followed by others
 // Implemented based on https://www.pagetable.com/?p=1135, https://github.com/mist64/cbmbus_doc
@@ -22,3 +24,6 @@ iec_tx_command_finalize:
 
 
 #endif // CONFIG_IEC
+
+
+#endif // ROM layout