Write to VI_V_CURRENT_LINE_REG

As of now, it's never being written to, so graphics plugins do not have
any access to that register. z64gl reads this register, so that's why it
has this screen shaking problem in certain games like Star Wars Rogue
Squadron.

Source/Project64/N64 System/Mips/Memory Virtual Mem.cpp

@@ -3426,6 +3426,7 @@ void CMipsMemoryVM::UpdateHalfLine()
 	m_HalfLine = (DWORD)(*g_NextTimer / g_System->ViRefreshRate());
 	m_HalfLine &= ~1;
 	m_HalfLine |= m_FieldSerration;
+	g_Reg->VI_V_CURRENT_LINE_REG = m_HalfLine;
 	m_HalfLineCheck = NextViTimer;
 }