drm/ttm: cleanup ttm_resource_compat

Move that function into the resource handling and remove an unused parameter.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210831112110.113196-1-christian.koenig@amd.com