drm/ttm: initialize the system domain with defaults v2

Instead of repeating that in each driver.

v2: keep the caching limitation for VMWGFX for now.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/382078/

drivers/gpu/drm/ttm/ttm_bo.c

@@ -1673,6 +1673,8 @@ int ttm_bo_device_init(struct ttm_bo_device *bdev,
 	 * Initialize the system memory buffer type.
 	 * Other types need to be driver / IOCTL initialized.
 	 */
+	bdev->man[TTM_PL_SYSTEM].available_caching = TTM_PL_MASK_CACHING;
+	bdev->man[TTM_PL_SYSTEM].default_caching = TTM_PL_FLAG_CACHED;
 	ret = ttm_bo_init_mm(bdev, TTM_PL_SYSTEM, 0);
 	if (unlikely(ret != 0))
 		goto out_no_sys;