drm/ttm: Define a single DRM_FILE_PAGE_OFFSET constant

Most TTM drivers define the constant DRM_FILE_PAGE_OFFSET of the same
value. The only exception is vboxvideo, which is being converted to the
new offset by this patch. Unifying the constants in a single place
simplifies the driver code.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/cirrus/cirrus_drv.h

@@ -169,7 +169,6 @@ cirrus_bo(struct ttm_buffer_object *bo)
 
 
 #define to_cirrus_obj(x) container_of(x, struct cirrus_gem_object, base)
-#define DRM_FILE_PAGE_OFFSET (0x100000000ULL >> PAGE_SHIFT)
 
 				/* cirrus_main.c */
 int cirrus_device_init(struct cirrus_device *cdev,