powerpc: e6500: Lock/unlock L2 cache instead of L1 as init_ram

MPC85xx has been using locked L1 cache as init_ram. L1 cache is a write
through cache on E6500. L2 cache is enabled to to hold the data. This
patch locks/unlocks L2 cache to ensure no data cast out from L2 cache.

Signed-off-by: York Sun <yorksun@freescale.com>
Reported-by: Jeffery Zhu <Jefferry.Zhu@freescale.com>

arch/powerpc/cpu/mpc85xx/start.S

@@ -1116,7 +1116,11 @@ switch_as:
 	li	r0,0
 1:
 	dcbz	r0,r3
-	dcbtls	0,r0,r3
+#ifdef CONFIG_E6500	/* Lock/unlock L2 cache instead of L1 */
+	dcbtls	2, r0, r3
+#else
+	dcbtls	0, r0, r3
+#endif
 	addi	r3,r3,CONFIG_SYS_CACHELINE_SIZE
 	bdnz	1b
 
@@ -1727,7 +1731,11 @@ unlock_ram_in_cache:
 	slwi	r4,r4,(10 - 1 - L1_CACHE_SHIFT)
 	mtctr	r4
 1:	dcbi	r0,r3
+#ifdef CONFIG_E6500	/* lock/unlock L2 cache instead of L1 */
+	dcblc	2, r0, r3
+#else
 	dcblc	r0,r3
+#endif
 	addi	r3,r3,CONFIG_SYS_CACHELINE_SIZE
 	bdnz	1b
 	sync