powerpc/83xx: fix build failure

Remove duplicated SDRAM_INTERVAL_BSTOPRE from mpc83xx.h,
which has been defined in fsl_ddr_sdram.h

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
diff --git a/include/mpc83xx.h b/include/mpc83xx.h
index a6d721a..b5a0bbf 100644
--- a/include/mpc83xx.h
+++ b/include/mpc83xx.h
@@ -1297,7 +1297,6 @@
  */
 #define SDRAM_INTERVAL_REFINT		0x3FFF0000
 #define SDRAM_INTERVAL_REFINT_SHIFT	16
-#define SDRAM_INTERVAL_BSTOPRE		0x00003FFF
 #define SDRAM_INTERVAL_BSTOPRE_SHIFT	0
 
 /*