drm/xe/bo: Remove unusued variable

bo is not used since all the checks are against tbo. Fix warning:

	../drivers/gpu/drm/xe/xe_bo.c: In function ‘xe_evict_flags’:
	../drivers/gpu/drm/xe/xe_bo.c:250:23: error: variable ‘bo’ set but not used [-Werror=unused-but-set-variable]
	  250 |         struct xe_bo *bo;
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_bo.c

@@ -247,8 +247,6 @@ int xe_bo_placement_for_flags(struct xe_device *xe, struct xe_bo *bo,
 static void xe_evict_flags(struct ttm_buffer_object *tbo,
 			   struct ttm_placement *placement)
 {
-	struct xe_bo *bo;
-
 	if (!xe_bo_is_xe_bo(tbo)) {
 		/* Don't handle scatter gather BOs */
 		if (tbo->type == ttm_bo_type_sg) {
@@ -265,8 +263,6 @@ static void xe_evict_flags(struct ttm_buffer_object *tbo,
 	 * For xe, sg bos that are evicted to system just triggers a
 	 * rebind of the sg list upon subsequent validation to XE_PL_TT.
 	 */
-
-	bo = ttm_to_xe_bo(tbo);
 	switch (tbo->resource->mem_type) {
 	case XE_PL_VRAM0:
 	case XE_PL_VRAM1: