powerpc/8xxx: Fix _POST_WORD_ADDR on 85xx & 86xx systems

We intended to use the PIC TFRR register however we where missing adding
in the PIC register base offset from IMMR when we defined
_POST_WORD_ADDR.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

include/post.h

@@ -58,11 +58,13 @@
 
 #elif defined (CONFIG_MPC85xx)
 #include <asm/immap_85xx.h>
-#define _POST_WORD_ADDR	(CONFIG_SYS_IMMR + offsetof(ccsr_pic_t, tfrr))
+#define _POST_WORD_ADDR	(CONFIG_SYS_IMMR + CONFIG_SYS_MPC85xx_PIC_OFFSET + \
+				offsetof(ccsr_pic_t, tfrr))
 
 #elif defined (CONFIG_MPC86xx)
 #include <asm/immap_86xx.h>
-#define _POST_WORD_ADDR	(CONFIG_SYS_IMMR + offsetof(ccsr_pic_t, tfrr))
+#define _POST_WORD_ADDR	(CONFIG_SYS_IMMR + CONFIG_SYS_MPC86xx_PIC_OFFSET + \
+				offsetof(ccsr_pic_t, tfrr))
 
 #elif defined (CONFIG_4xx)
 #define _POST_WORD_ADDR \