nfit: Fix the check for a successful NFIT merge

Missed previously due to a lack of test coverage on a platform that
provided an valid response to _FIT.
Signed-off-by: Linda Knippers <linda.knippers@hpe.com>
Acked-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit.c

@@ -1816,7 +1816,7 @@ static void acpi_nfit_notify(struct acpi_device *adev, u32 event)
 	nfit_saved = acpi_desc->nfit;
 	acpi_desc->nfit = (struct acpi_table_nfit *)buf.pointer;
 	ret = acpi_nfit_init(acpi_desc, buf.length);
-	if (!ret) {
+	if (ret) {
 		/* Merge failed, restore old nfit, and exit */
 		acpi_desc->nfit = nfit_saved;
 		dev_err(dev, "failed to merge updated NFIT\n");