powerpc: Add includes to fix powernv/rng.c build

Caused by commit a4da0d50 ("powerpc: Implement
arch_get_random_long/int() for powernv") from the powerpc tree
interacting with commit b5b4bb3f ("of: only include prom.h on sparc")
from the dt-rh tree.

I added this merge fix patch (which will need to be sent to Linus when
these two trees get merged, or could be applied now to the powerpc tree):

[ Also add linux/smp.h to get cpu_to_chip_id -- BenH ]
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: NRob Herring <rob.herring@calxeda.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/powernv/rng.c

@@ -11,10 +11,13 @@
 
 #include <linux/kernel.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_platform.h>
 #include <linux/slab.h>
+#include <linux/smp.h>
 #include <asm/archrandom.h>
 #include <asm/io.h>
+#include <asm/prom.h>
 #include <asm/machdep.h>