Added AMI 386DX and MR 386DX models (both based on OPTi 495 chipset). AMI 386DX supports external cache, useful for with prefetch emulation.

Also commit a few fixes required :
- Set EDX correctly on soft reset
- LOCK NOP is now treated as an illegal instruction
- Tweaks to FDC sense interrupt handling following FDC reset

src/ps1.c

@@ -213,7 +213,10 @@ void ps1_m2121_write(uint16_t port, uint8_t val, void *p)
         {
                 case 0x0092:
                 if (val & 1)
+                {
                         softresetx86();
+                        cpu_set_edx();
+                }
                 ps1_92 = val & ~1;
                 mem_a20_alt = val & 2;
                 mem_a20_recalc();