ACPI: Only count valid srat memory structures

Otherwise you could run into:
WARN_ON in numa_register_memblks(), because node_possible_map is zero

References: https://bugzilla.novell.com/show_bug.cgi?id=757888

On this machine (ProLiant ML570 G3) the SRAT table contains:
  - No processor affinities
  - One memory affinity structure (which is set disabled)

CC: Per Jessen <per@opensuse.org>
CC: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index 2a63993..cb31298 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -237,6 +237,8 @@
 	return 0;
 }
 
+static int __initdata parsed_numa_memblks;
+
 static int __init
 acpi_parse_memory_affinity(struct acpi_subtable_header * header,
 			   const unsigned long end)
@@ -250,8 +252,8 @@
 	acpi_table_print_srat_entry(header);
 
 	/* let architecture-dependent part to do it */
-	acpi_numa_memory_affinity_init(memory_affinity);
-
+	if (!acpi_numa_memory_affinity_init(memory_affinity))
+		parsed_numa_memblks++;
 	return 0;
 }
 
@@ -306,7 +308,7 @@
 
 	if (cnt < 0)
 		return cnt;
-	else if (cnt == 0)
+	else if (!parsed_numa_memblks)
 		return -ENOENT;
 	return 0;
 }