drm/selftests: missing error code in igt_buddy_alloc_smoke()

Set the error code to -ENOMEM if drm_random_order() fails.

Fixes: e6ff5ef81170 ("drm/selftests: add drm buddy smoke testcase")
Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Arunpravin <[e-mail]>
Signed-off-by: Christian König <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/20220307125458.GA16710@kili

drivers/gpu/drm/selftests/test-drm_buddy.c

···
 	}
 
 	order = drm_random_order(mm.max_order + 1, &prng);
-	if (!order)
+	if (!order) {
+		err = -ENOMEM;
 		goto out_fini;
+	}
 
 	for (i = 0; i <= mm.max_order; ++i) {
 		struct drm_buddy_block *block;