Add NVR on Epson Equity LT

It's a HD146818 chip mapped at 11B4h-11B5h. The century byte is at 1Ah.
The IRQ line doesn't seem to be hooked on.

src/include/86box/nvr.h

@@ -97,6 +97,7 @@ extern const device_t ami_1994_nvr_device;
 extern const device_t ami_1995_nvr_device;
 extern const device_t via_nvr_device;
 extern const device_t p6rp4_nvr_device;
+extern const device_t elt_nvr_device;
 #endif
 
 extern void rtc_tick(void);