coreboot t132: Stop running AVP at the end of romstage

Stop running AVP at the end of romstage until event conditions are met (JTAG,
GIC_IRQ or LIC_IRQ).

BUG=chrome-os-partner:30831
BRANCH=None
TEST=Compiles successfully and boots till last known good checkpoint.

Change-Id: Ia221f08b27ac0c60a66d588e351677144cc6a322
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://chromium-review.googlesource.com/209424
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Commit-Queue: Furquan Shaikh <furquan@chromium.org>

src/soc/nvidia/tegra132/romstage.c

@@ -28,6 +28,8 @@
 #include "sdram.h"
 #include "ccplex.h"
 
+#include <soc/clock.h>
+
 void romstage(void);
 void romstage(void)
 {
@@ -70,5 +72,5 @@ void romstage(void)
 
 	ccplex_cpu_start(entry);
 
-	while (1);
+	clock_halt_avp();
 }