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>

drivers/net/ethernet/ibm/emac/mal.c

@@ -27,6 +27,7 @@
 
 #include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/of_irq.h>
 
 #include "core.h"
 #include <asm/dcr-regs.h>