driver-core: Add device node pointer to struct device

Currently, platforms using CONFIG_OF add a 'struct device_node *of_node'
to dev->archdata.  However, with CONFIG_OF becoming generic for all
architectures, it makes sense for commonality to move it out of archdata
and into struct device proper.

This patch adds a struct device_node *of_node member to struct device
and updates all locations which currently write the device_node pointer
into archdata to also update dev->of_node.  Subsequent patches will
modify callers to use the archdata location and ultimately remove
the archdata member entirely.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
CC: Michal Simek <monstr@monstr.eu>
CC: Greg Kroah-Hartman <gregkh@suse.de>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: "David S. Miller" <davem@davemloft.net>
CC: Stephen Rothwell <sfr@canb.auug.org.au>
CC: Jeremy Kerr <jeremy.kerr@canonical.com>
CC: microblaze-uclinux@itee.uq.edu.au
CC: linux-kernel@vger.kernel.org
CC: linuxppc-dev@ozlabs.org
CC: sparclinux@vger.kernel.org