tools/testing/cxl: Move cxl_test resources to the top of memory

A recent QEMU upgrade resulted in collisions between QEMU's chosen
location for PCI MMIO and cxl_test's fake address location for emulated
CXL purposes. This was great for testing resource collisions, but not so
great for continuing to test the nominal cases. Move cxl_test to the
top-of-memory where it is less likely to collide with other resources.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/165603886021.551046.12395967874222763381.stgit@dwillia2-xfhSigned-off-by: Dan Williams <dan.j.williams@intel.com>

tools/testing/cxl/test/cxl.c

@@ -619,7 +619,8 @@ static __init int cxl_test_init(void)
 		goto err_gen_pool_create;
 	}
 
-	rc = gen_pool_add(cxl_mock_pool, SZ_512G, SZ_64G, NUMA_NO_NODE);
+	rc = gen_pool_add(cxl_mock_pool, iomem_resource.end + 1 - SZ_64G,
+			  SZ_64G, NUMA_NO_NODE);
 	if (rc)
 		goto err_gen_pool_add;