tools/testing/cxl: require 64-bit

size_t is limited to 32-bits and so the gen_pool_alloc() using
the size of SZ_64G would map to 0, triggering a low allocation
which is not expected. Force the dependency on 64-bit for cxl_test
as that is what it was designed for.

This issue was found by build test reports when converting this
driver as a proper upstream driver.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20221219195050.325959-1-mcgrof@kernel.orgSigned-off-by: Dan Williams <dan.j.williams@intel.com>

tools/testing/cxl/config_check.c

@@ -7,6 +7,7 @@ void check(void)
 	 * These kconfig symbols must be set to "m" for cxl_test to load
 	 * and operate.
 	 */
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_64BIT));
 	BUILD_BUG_ON(!IS_MODULE(CONFIG_CXL_BUS));
 	BUILD_BUG_ON(!IS_MODULE(CONFIG_CXL_ACPI));
 	BUILD_BUG_ON(!IS_MODULE(CONFIG_CXL_PMEM));