of: Fix dereferencing node name in debug output to be safe

Several locations in the of_address and of_irq code dereference the
full_name parameter from a device_node pointer without checking if the
pointer is valid.  This patch switches to use of_node_full_name() which
always checks the pointer.

Signed-off-by: Grant Likely <grant.likely@linaro.org>

diff --cc drivers/of/address.c
Simple merge

diff --cc drivers/of/irq.c
Simple merge