Improvements to the OPTi 597 machine.

- Add emulation of the FDC37C661 Super I/O
- Fix Pentium VLB timing (was running VLB at 2x bus speed instead of 1/2 bus speed)
- Fix the cache register on the OPTi 5x7 chipset
- The actual minimum RAM amount is 2 MB, not 1 MB.
- Fix chipset naming consistency

src/machine/m_at_socket4_5.c

@@ -54,7 +54,7 @@ machine_at_excalibur_init(const machine_t *model)
 
     device_add(&ide_vlb_device);
     device_add(&opti5x7_device);
-    device_add(&fdc37c663_device);
+    device_add(&fdc37c661_device);
     device_add(&keyboard_at_ami_device);
 
     return ret;