ymfm_opn: OPNA does not have 4 latches

Author: happppp

3rdparty/ymfm/src/ymfm_opn.cpp

@@ -143,15 +143,13 @@ bool opn_registers_base<IsOpnA>::write(uint16_t index, uint8_t data, uint32_t &c
 	assert(index < REGISTERS);
 
 	// writes in the 0xa0-af/0x1a0-af region are handled as latched pairs
-	// borrow unused registers 0xb8-bf/0x1b8-bf as temporary holding locations
+	// borrow unused registers 0xb8-bf as temporary holding locations
 	if ((index & 0xf0) == 0xa0)
 	{
 		if (bitfield(index, 0, 2) == 3)
 			return false;
 
 		uint32_t latchindex = 0xb8 | bitfield(index, 3);
-		if (IsOpnA)
-			latchindex |= index & 0x100;
 
 		// writes to the upper half just latch (only low 6 bits matter)
 		if (bitfield(index, 2))