powerpc: chrp: Use of_node_is_type to access device_type

Commit 8ce5f841 ("of: Remove struct device_node.type pointer")
removed struct device_node.type pointer, but the conversion to use
of_node_is_type() accessor was missed in chrp_init_IRQ().

Fixes: 8ce5f841

 ("of: Remove struct device_node.type pointer")
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Rob Herring <robh@kernel.org>