powerpc/pmac: Fix DT refcount imbalance in pmac_pic_probe_oldstyle

Internally, of_find_node_by_name() calls of_node_put() on its "from"
parameter, which must not be done on "master", as it's still in use, and
will be released manually later.  This may cause a zero kref refcount.

Call of_node_get() before to compensate for this.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/powermac/pic.c

@@ -321,6 +321,9 @@ static void __init pmac_pic_probe_oldstyle(void)
 		max_irqs = max_real_irqs = 64;
 
 		/* We might have a second cascaded heathrow */
+
+		/* Compensate for of_node_put() in of_find_node_by_name() */
+		of_node_get(master);
 		slave = of_find_node_by_name(master, "mac-io");
 
 		/* Check ordering of master & slave */