ACPI: Ingore the memory block with zero block size in course of memory hotplug

If the memory block size is zero, ignore it and don't do the memory hotplug
flowchart. Otherwise it will complain the following warning message:
  >System RAM resource 0 - ffffffffffffffff cannot be added
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/acpi_memhotplug.c

@@ -242,7 +242,12 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 			num_enabled++;
 			continue;
 		}
-
+		/*
+		 * If the memory block size is zero, please ignore it.
+		 * Don't try to do the following memory hotplug flowchart.
+		 */
+		if (!info->length)
+			continue;
 		if (node < 0)
 			node = memory_add_physaddr_to_nid(info->start_addr);
 
@@ -257,8 +262,15 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 		mem_device->state = MEMORY_INVALID_STATE;
 		return -EINVAL;
 	}
-
-	return result;
+	/*
+	 * Sometimes the memory device will contain several memory blocks.
+	 * When one memory block is hot-added to the system memory, it will
+	 * be regarded as a success.
+	 * Otherwise if the last memory block can't be hot-added to the system
+	 * memory, it will be failure and the memory device can't be bound with
+	 * driver.
+	 */
+	return 0;
 }
 
 static int acpi_memory_powerdown_device(struct acpi_memory_device *mem_device)