ppc: Conditionally compile bat_rw.c

Only a few PPC boards actually use the common BAT manipulation
functions, so only compile it for them.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/include/configs/sbc8641d.h b/include/configs/sbc8641d.h
index a7831c0..490d4f5 100644
--- a/include/configs/sbc8641d.h
+++ b/include/configs/sbc8641d.h
@@ -64,6 +64,7 @@
 #define CONFIG_TSEC_ENET		/* tsec ethernet support */
 #define CONFIG_ENV_OVERWRITE
 
+#define CONFIG_BAT_RW		1	/* Use common BAT rw code */
 #define CONFIG_HIGH_BATS	1	/* High BATs supported and enabled */
 
 #undef CONFIG_SPD_EEPROM		/* Do not use SPD EEPROM for DDR setup*/