Move extern into video.h (part 2)

src/machine/m_at_socket370.c

@@ -355,7 +355,6 @@ machine_at_awo671r_init(const machine_t *model)
     device_add(&keyboard_ps2_pci_device);
     device_add(&sst_flash_39sf020_device);
     if (gfxcard[0] == VID_INTERNAL) {
-        extern const device_t chips_69000_onboard_device;
         device_add(&chips_69000_onboard_device);
     }
     spd_register(SPD_TYPE_SDRAM, 0x3, 256);