of: Convert to using %pOFn instead of device_node.name

In preparation to remove the node name pointer from struct device_node,
convert printf users to use the %pOFn format specifier.

Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>