IF386AX: Set video card to fixed and make the power off function actually power off.

src/machine/m_at_286_386sx.c

@@ -658,8 +658,8 @@ machine_at_if386sx_init(const machine_t *model)
 
     device_add(&neat_sx_device);
 
-    if (gfxcard[0] == VID_INTERNAL)
     device_add(&if386jega_device);
+
     if (fdc_current[0] == FDC_INTERNAL)
         device_add(&fdc_at_device);
 

src/machine/machine_table.c

@@ -4768,7 +4768,7 @@ const machine_t machines[] = {
             .max_multi = 0
         },
         .bus_flags = MACHINE_AT,
-        .flags = MACHINE_VIDEO,
+        .flags = MACHINE_VIDEO_FIXED,
         .ram = {
             .min = 1024,
             .max = 4096,

src/video/vid_jega.c

@@ -28,6 +28,7 @@
 #include <86box/timer.h>
 #include <86box/pic.h>
 #include <86box/pit.h>
+#include <86box/plat.h>
 #include <86box/mem.h>
 #include <86box/rom.h>
 #include <86box/device.h>
@@ -800,9 +801,11 @@ if386_p6x_write(uint16_t port, uint8_t val, void *priv)
             }
             jega_recalctimings(jega);
         } else if (p65idx == 0x05) {
-            if (val & 0x10) { /* Power off (instead this call hardware reset here) */
-                resetx86();
-            }
+            if (val & 0x10)
+                /* Power off (instead this call hardware reset here) */
+                // resetx86();
+                /* Actually, power off - we have a function for that! */
+                plat_power_off();
         }
     }
     return;