x86, e820: add support for AddressRangeUnusuable ACPI memory type

Add support for the E820_UNUSABLE memory type, which is defined in
Revision 3.0b (Oct.  10, 2006) of the ACPI Specification on p.  394 Table
14-1:

  AddressRangeUnusuable This range of address contains memory in which
  errors have been detected.  This range must not be used by the OSPM.

Signed-off-by: Joseph Cihula <joseph.cihula@intel.com>
Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: Gang Wei <gang.wei@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/e820.c

@@ -148,6 +148,9 @@ void __init e820_print_map(char *who)
 		case E820_NVS:
 			printk(KERN_CONT "(ACPI NVS)\n");
 			break;
+		case E820_UNUSABLE:
+			printk("(unusable)\n");
+			break;
 		default:
 			printk(KERN_CONT "type %u\n", e820.map[i].type);
 			break;
@@ -1260,6 +1263,7 @@ static inline const char *e820_type_to_string(int e820_type)
 	case E820_RAM:	return "System RAM";
 	case E820_ACPI:	return "ACPI Tables";
 	case E820_NVS:	return "ACPI Non-volatile Storage";
+	case E820_UNUSABLE:	return "Unusable memory";
 	default:	return "reserved";
 	}
 }

include/asm-x86/e820.h

@@ -43,6 +43,7 @@
 #define E820_RESERVED	2
 #define E820_ACPI	3
 #define E820_NVS	4
+#define E820_UNUSABLE	5
 
 /* reserved RAM used by kernel itself */
 #define E820_RESERVED_KERN        128