TMS: Enable support for using VSYNC interrupt

Use the VSYNC interrupt to trigger the sys timer event

Source/HBIOS/std.asm

@@ -186,6 +186,7 @@ AYMODE_RCZ180	.EQU	4		; RC2014 SOUND MODULE BY ED BRINDLEY ON Z180
 TMSMODE_NONE	.EQU	0
 TMSMODE_SCG	.EQU	1		; SCG ECB BOARD
 TMSMODE_N8	.EQU	2		; N8 BUILT-IN VIDEO
+TMSMODE_RC2014	.EQU	3		; RC2014 BUILT-IN VIDEO
 ;
 ; SERIAL DEVICE CONFIGURATION CONSTANTS
 ;