fs/openpromfs: use full_name instead of path_component_name

In preparation to remove struct device_node.path_component_name, use
full_name instead. kbasename is used so full_name can be used whether it
is the full path or just the node's name and unit-address.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>