sb/intel/{bd82x6,ibexpeak}: Move RCBA macros to a common location

Many generations of Intel hardware have identical code concerning the
RCBA.

Change-Id: I33ec6801b115c0d64de1d2a0dc5d439186f3580a
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/23287
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/southbridge/intel/ibexpeak/lpc.c

@@ -35,6 +35,7 @@
 #include "pch.h"
 #include "nvs.h"
 #include <southbridge/intel/common/pciehp.h>
+#include <southbridge/intel/common/rcba.h>
 
 #define NMI_OFF	0