nfit: skip region registration for incomplete control regions

Per the ACPI specification the only functional purpose for a DIMM
Control Region to be mapped into the system physical address space, from
an OSPM perspective, is to support block-apertures. However, there are
some BIOSen that publish DIMM Control Region SPA entries for pre-boot
environment consumption.  Undo the kernel policy of generating disabled
'ndblk' regions when this configuration is detected.

Cc: <stable@vger.kernel.org>
Fixes: 1f7df6f8 ("libnvdimm, nfit: regions (block-data-window...)")
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -2578,7 +2578,7 @@ static int acpi_nfit_init_mapping(struct acpi_nfit_desc *acpi_desc,
 	struct acpi_nfit_system_address *spa = nfit_spa->spa;
 	struct nd_blk_region_desc *ndbr_desc;
 	struct nfit_mem *nfit_mem;
-	int blk_valid = 0, rc;
+	int rc;
 
 	if (!nvdimm) {
 		dev_err(acpi_desc->dev, "spa%d dimm: %#x not found\n",
@@ -2598,15 +2598,14 @@ static int acpi_nfit_init_mapping(struct acpi_nfit_desc *acpi_desc,
 		if (!nfit_mem || !nfit_mem->bdw) {
 			dev_dbg(acpi_desc->dev, "spa%d %s missing bdw\n",
 					spa->range_index, nvdimm_name(nvdimm));
-		} else {
-			mapping->size = nfit_mem->bdw->capacity;
-			mapping->start = nfit_mem->bdw->start_address;
-			ndr_desc->num_lanes = nfit_mem->bdw->windows;
-			blk_valid = 1;
+			break;
 		}
 
+		mapping->size = nfit_mem->bdw->capacity;
+		mapping->start = nfit_mem->bdw->start_address;
+		ndr_desc->num_lanes = nfit_mem->bdw->windows;
 		ndr_desc->mapping = mapping;
-		ndr_desc->num_mappings = blk_valid;
+		ndr_desc->num_mappings = 1;
 		ndbr_desc = to_blk_region_desc(ndr_desc);
 		ndbr_desc->enable = acpi_nfit_blk_region_enable;
 		ndbr_desc->do_io = acpi_desc->blk_do_io;