Replaced the S2DGE with the GA-6DXU

More stable and has everything we emulate other than it's On-Board SCSI. Works as intended.

src/include/86box/machine.h

@@ -356,9 +356,7 @@ extern const device_t 	*at_tsunamiatx_get_device(void);
 #endif
 
 /* m_at_slot2.c */
-#if defined(DEV_BRANCH) && defined(NO_SIO)
-extern int	machine_at_s2dge_init(const machine_t *);
-#endif
+extern int	machine_at_6gxu_init(const machine_t *);
 
 /* m_at_socket370.c */
 extern int	machine_at_s370slm_init(const machine_t *);