x86: Change MMIO addr in readN(addr)/writeN(addr, val) to pointer

On x86, change the type of the address parameter in
read8()/read16/read32()/write8()/write16()/write32() to be a
pointer, instead of unsigned long.

Change-Id: Ic26dd8a72d82828b69be3c04944710681b7bd330
Signed-off-by: Kevin Paul Herbert <kph@meraki.net>
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/7784
Tested-by: build bot (Jenkins)
diff --git a/src/mainboard/samsung/lumpy/devicetree.cb b/src/mainboard/samsung/lumpy/devicetree.cb
index 9b0fc40..0372614 100644
--- a/src/mainboard/samsung/lumpy/devicetree.cb
+++ b/src/mainboard/samsung/lumpy/devicetree.cb
@@ -112,7 +112,7 @@
 				     register "have_isa_interrupts" = "1"
 				     register "irq_on_fsb" = "1"
 				     register "enable_virtual_wire" = "1"
-				     register "base" = "0xfec00000"
+				     register "base" = "(void *)0xfec00000"
 				     device ioapic 4 on end
 				end
 			end