drivers: clean-up prom.h implicit includes

Powerpc is a mess of implicit includes by prom.h. Add the necessary
explicit includes to drivers in preparation of prom.h cleanup.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Grant Likely <grant.likely@linaro.org>
diff --git a/sound/ppc/pmac.c b/sound/ppc/pmac.c
index c93fbbb..7a43c0c 100644
--- a/sound/ppc/pmac.c
+++ b/sound/ppc/pmac.c
@@ -28,6 +28,8 @@
 #include <linux/interrupt.h>
 #include <linux/pci.h>
 #include <linux/dma-mapping.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
 #include <sound/core.h>
 #include "pmac.h"
 #include <sound/pcm_params.h>