drivers/block/pmem: Add a driver for persistent memory

drivers/block/pmem: Add a driver for persistent memory

PMEM is a new driver that presents a reserved range of memory as
a block device.  This is useful for developing with NV-DIMMs,
and can be used with volatile memory as a development platform.

This patch contains the initial driver from Ross Zwisler, with
various changes: converted it to use a platform_device for
discovery, fixed partition support and merged various patches
from Boaz Harrosh.

Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-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/1427872339-6688-3-git-send-email-hch@lst.de
[ Minor cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>