of: remove /proc/device-tree

of: remove /proc/device-tree

The same data is now available in sysfs, so we can remove the code
that exports it in /proc and replace it with a symlink to the sysfs
version.

Tested on versatile qemu model and mpc5200 eval board. More testing
would be appreciated.

v5: Fixed up conflicts with mainline changes

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
(cherry picked from commit 8357041a69b368991d1b04d9f1d297f8d71e1314)
Signed-off-by: Mark Brown <broonie@kernel.org>
Conflicts:
	drivers/of/base.c
	fs/proc/proc_devtree.c
	include/linux/of.h