nouveau/winsys: Getch the BAR size from the kernel

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26622>

src/nouveau/headers/nv_device_info.h

@@ -43,6 +43,7 @@ struct nv_device_info {
    uint16_t cls_compute;
 
    uint64_t vram_size_B;
+   uint64_t bar_size_B;
 };
 
 #endif /* NV_DEVINFO_H */

src/nouveau/winsys/nouveau_device.c

@@ -317,6 +317,10 @@ nouveau_ws_device_new(drmDevicePtr drm_device)
    else
       device->local_mem_domain = NOUVEAU_GEM_DOMAIN_VRAM;
 
+   if (drm_device->bustype == DRM_BUS_PCI &&
+       !nouveau_ws_param(fd, NOUVEAU_GETPARAM_VRAM_BAR_SIZE, &value))
+      device->info.bar_size_B = value;
+
    if (nouveau_ws_param(fd, NOUVEAU_GETPARAM_GRAPH_UNITS, &value))
       goto out_err;