tools/testing/cxl: Require CONFIG_DEBUG_FS

The cxl_mem driver uses debugfs to support poison inject and clear.
Add debugfs to the list of required symbols so that cxl_test can
emulate those poison operations.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/4f3aab57fbf1cc3ccde2eb887c5d90566c8d0e90.1681874357.git.alison.schofield@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: AlisonSchofield

tools/testing/cxl/config_check.c

@@ -13,4 +13,5 @@ void check(void)
 	BUILD_BUG_ON(!IS_MODULE(CONFIG_CXL_PMEM));
 	BUILD_BUG_ON(!IS_ENABLED(CONFIG_CXL_REGION_INVALIDATION_TEST));
 	BUILD_BUG_ON(!IS_ENABLED(CONFIG_NVDIMM_SECURITY_TEST));
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_DEBUG_FS));
 }