SPD improvements

* Word and block read support for the SMBus ROM
* Asymmetric module support to cover more RAM configurations
* Add 86Box version as revision code
* Fix supported CAS latencies
* Fixed slot count on the GA-6BXC

src/machine/m_at_slot1.c

@@ -114,7 +114,7 @@ machine_at_6bxc_init(const machine_t *model)
     device_add(&keyboard_ps2_pci_device);
     device_add(&um8669f_device); /*ITE 8671*/
     device_add(&sst_flash_39sf020_device);
-    spd_register(SPD_TYPE_SDRAM, 0xF, 256);    
+    spd_register(SPD_TYPE_SDRAM, 0x7, 256);    
 
     return ret;
 }