Change DDR tlb start entry to CONFIG param for 85xx

So that we can locate the DDR tlb start entry to the value other than 8. By
default, it is still 8.

Signed-off-by: Haiying Wang <Haiying.Wang@freescale.com>
diff --git a/cpu/mpc85xx/tlb.c b/cpu/mpc85xx/tlb.c
index 5b5f791..25fa9ee 100644
--- a/cpu/mpc85xx/tlb.c
+++ b/cpu/mpc85xx/tlb.c
@@ -125,6 +125,10 @@
 }
 #endif
 
+#ifndef CONFIG_SYS_DDR_TLB_START
+#define CONFIG_SYS_DDR_TLB_START 8
+#endif
+
 unsigned int setup_ddr_tlbs(unsigned int memsize_in_meg)
 {
 	unsigned int tlb_size;
@@ -171,7 +175,7 @@
 	 * Configure DDR TLB1 entries.
 	 * Starting at TLB1 8, use no more than 8 TLB1 entries.
 	 */
-	ram_tlb_index = 8;
+	ram_tlb_index = CONFIG_SYS_DDR_TLB_START;
 	ram_tlb_address = (unsigned int)CONFIG_SYS_DDR_SDRAM_BASE;
 	while (ram_tlb_address < (memsize_in_meg * 1024 * 1024)
 	      && ram_tlb_index < 16) {