of/irq: Fix device_node refcount in of_irq_parse_raw()

Commit 23616132

, "of/irq: Refactor interrupt-map parsing" changed
the refcount on the device_node causing an error in of_node_put():

ERROR: Bad of_node_put() on /pci@800000020000000
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc3-dirty #2
Call Trace:
[c00000003e403500] [c0000000000144fc] .show_stack+0x7c/0x1f0 (unreliable)
[c00000003e4035d0] [c00000000070f250] .dump_stack+0x88/0xb4
[c00000003e403650] [c0000000005e8768] .of_node_release+0xd8/0xf0
[c00000003e4036e0] [c0000000005eeafc] .of_irq_parse_one+0x10c/0x280
[c00000003e4037a0] [c0000000005efd4c] .of_irq_parse_pci+0x3c/0x1d0
[c00000003e403840] [c000000000038240] .pcibios_setup_device+0xa0/0x2e0
[c00000003e403910] [c0000000000398f0] .pcibios_setup_bus_devices+0x60/0xd0
[c00000003e403990] [c00000000003b3a4] .__of_scan_bus+0x1a4/0x2b0
[c00000003e403a80] [c00000000003a62c] .pcibios_scan_phb+0x30c/0x410
[c00000003e403b60] [c0000000009fe430] .pcibios_init+0x7c/0xd4

This patch adjusts the refcount in the walk of the interrupt tree.
When a match is found, there is no need to increase the refcount
on 'out_irq->np' as 'newpar' is already holding a ref. The refcount
balance between 'ipar' and 'newpar' is maintained in the skiplevel:
goto label.

This patch also removes the usage of the device_node variable 'old'
which seems useless after the latest changes.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>