x86/mm: Add support for the non-standard protected e820 type

Various recent BIOSes support NVDIMMs or ADR using a
non-standard e820 memory type, and Intel supplied reference
Linux code using this type to various vendors.

Wire this e820 table type up to export platform devices for the
pmem driver so that we can use it in Linux.

Based on earlier work from:

   Dave Jiang <dave.jiang@intel.com>
   Dan Williams <dan.j.williams@intel.com>

Includes fixes for NUMA regions from Boaz Harrosh.

Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-nvdimm@ml01.01.org
Link: http://lkml.kernel.org/r/1427872339-6688-2-git-send-email-hch@lst.de
[ Minor cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/uapi/asm/e820.h

@@ -33,6 +33,16 @@
 #define E820_NVS	4
 #define E820_UNUSABLE	5
 
+/*
+ * This is a non-standardized way to represent ADR or NVDIMM regions that
+ * persist over a reboot.  The kernel will ignore their special capabilities
+ * unless the CONFIG_X86_PMEM_LEGACY=y option is set.
+ *
+ * ( Note that older platforms also used 6 for the same type of memory,
+ *   but newer versions switched to 12 as 6 was assigned differently.  Some
+ *   time they will learn... )
+ */
+#define E820_PRAM	12
 
 /*
  * reserved RAM used by kernel itself