Fixed PS/2 mouse to PCI (PIIX) wiring, fixes recently introduced PS/2 mouse hangs;

The AT keyboard "write to mouse" command now returns 0xFF (error) when no PS/2 mouse is attached - fixes hangs on AOpen AP53, ASUS P/I-P55T2S, and Tyan Titan Pro/ATX when not using PS/2 mouse;
Fixed the emulation of the SMC FDC37C669 Super I/O chip - serial ports now work correctly on the AOpen AP53 and the ASUS P/I-P55T2S.

src/mouse_ps2.c

@@ -127,7 +127,7 @@ void mouse_ps2_write(uint8_t val, void *p)
                         keyboard_at_adddata_mouse(0xaa);
                         keyboard_at_adddata_mouse(0x00);
                         break;
-                        
+
 //                        default:
 //                        fatal("mouse_ps2 : Bad command %02X\n", val, mouse->command);
                 }