drm/tests: shmem: Fix memleak

The drm_gem_shmem_test_get_pages_sgt() gets a scatter-gather table using
the drm_gem_shmem_get_sg_table() function and rightfully calls
sg_free_table() on it. However, it's also supposed to kfree() the
returned sg_table, but doesn't.

This leads to a memory leak, reported by kmemleak. Fix it by adding a
kunit action to kfree the sgt when the test ends.

Reported-by: Philipp Stanner <phasta@mailbox.org>
Closes: https://lore.kernel.org/dri-devel/a7655158a6367ac46194d57f4b7433ef0772a73e.camel@mailbox.org/
Fixes: 93032ae ("drm/test: add a test suite for GEM objects backed by shmem")
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250408140758.1831333-1-mripard@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

Author: mripard

drivers/gpu/drm/tests/drm_gem_shmem_test.c

@@ -216,6 +216,9 @@ static void drm_gem_shmem_test_get_pages_sgt(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, sgt);
 	KUNIT_EXPECT_NULL(test, shmem->sgt);
 
+	ret = kunit_add_action_or_reset(test, kfree_wrapper, sgt);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
 	ret = kunit_add_action_or_reset(test, sg_free_table_wrapper, sgt);
 	KUNIT_ASSERT_EQ(test, ret, 0);