PPC4xx: Minimal changes to add vxWorks support

Signed-off-by: Niklaus Giger <niklaus.giger@netstal.com>
diff --git a/cpu/ppc4xx/start.S b/cpu/ppc4xx/start.S
index f5a135f..645ac0b 100644
--- a/cpu/ppc4xx/start.S
+++ b/cpu/ppc4xx/start.S
@@ -1356,7 +1356,11 @@
 	dccci	0,0			/* Invalidate data cache, now no longer our stack */
 	sync
 	isync
-	addi	r1,r0,0x0000		/* TLB entry #0 */
+#ifdef CFG_TLB_FOR_BOOT_FLASH
+	addi	r1,r0,CFG_TLB_FOR_BOOT_FLASH	/* Use defined TLB */
+#else
+	addi	r1,r0,0x0000		/* Default TLB entry is #0 */
+#endif
 	tlbre	r0,r1,0x0002		/* Read contents */
 	ori	r0,r0,0x0c00		/* Or in the inhibit, write through bit */
 	tlbwe	r0,r1,0x0002		/* Save it out */