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/cpu/intel/model_206ax/bootblock.c

@@ -28,6 +28,7 @@
 	IS_ENABLED(CONFIG_SOUTHBRIDGE_INTEL_C216)
 /* Needed for RCBA access to set Soft Reset Data register */
 #include <southbridge/intel/bd82x6x/pch.h>
+#include <southbridge/intel/common/rcba.h>
 #else
 #error "CPU must be paired with Intel BD82X6X or C216 southbridge"
 #endif