85xx: Add support for additional e500mc features

* Enable backside L2
* e500mc no longer has timebase enable in HID (moved to CCSR register)

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/cpu/mpc85xx/start.S b/cpu/mpc85xx/start.S
index 80f9677..89eea8c 100644
--- a/cpu/mpc85xx/start.S
+++ b/cpu/mpc85xx/start.S
@@ -161,7 +161,9 @@
 #if defined(CONFIG_ENABLE_36BIT_PHYS)
 	ori	r0,r0,HID0_ENMAS7@l	/* Enable MAS7 */
 #endif
+#ifndef CONFIG_E500MC
 	ori	r0,r0,HID0_TBEN@l	/* Enable Timebase */
+#endif
 	mtspr	HID0,r0
 
 #ifndef CONFIG_E500MC