[MTD] of_device-based physmap driver

inlined below is the patch that adds physmap driver for of_device.
It's an MTD part of the two-part support for flash/ROM devices based
on Open Firmware descriptions. The arch part (currently only PowerPC
which is no surprise) was introduced to powerpc folks earlier and
recently the older version of the powerpc part has been included into
the powerpc.git tree
(see http://www.kernel.org/git/?p=linux/kernel/git/paulus/powerpc.git;a=commitdiff;h=28f9ec349ae47c91768b7bc5607db4442c818e11

).

 drivers/mtd/maps/Kconfig      |    9 +
 drivers/mtd/maps/Makefile     |    1
 drivers/mtd/maps/physmap_of.c |  255 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 265 insertions(+)

Signed-off-by: Vitaly Wool <vwool@ru.mvista.com>
Signed-off-by: Sergey Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>