hp9k_3xx: fix RTC corruption

pre-init the latch clock variable to 1, so the first write to the latch
doesn't cause invalid data latched which would trigger an invalid write to
the RTC, causing an invalid time.

src/devices/bus/hp_dio/human_interface.cpp

@@ -138,6 +138,7 @@ void human_interface_device::device_reset()
 	m_ppoll_sc = 0;
 	m_gpib_irq_line = false;
 	m_kbd_nmi = false;
+	m_old_latch_enable = true;
 	m_rtc->cs1_w(ASSERT_LINE);
 	m_rtc->cs2_w(CLEAR_LINE);
 	m_rtc->write_w(CLEAR_LINE);