cr50: print '.' every time cr50 resumes from sleep

Right now there is no way to verify cr50 is asleep just by looking at
the UART output. You can check by running taskinfo and seeing that the
GC_IRQNUM_PMU_INTR_WAKEUP_INT irq count has increased or by measuring
cr50 power.

In the past we have had Cr50 issues that we think are related to sleep.
Devices like poppy will have the Cr50 uart connected to servo, so we can
capture the Cr50 console output. It would be helpful if there was an
easy way to tell that cr50 is asleep from the UART output to more easily
confirm issues might be related to sleep. This change will print '.'
every time Cr50 resumes from sleep. Cr50 wakes up every half second for
HOOK_TICK, so with this change '.' prints every half second while cr50
is asleep.

BUG=none
BRANCH=none
TEST=boot a device, wait a while, and verify cr50 starts printing '.'
every half second. Turn off the device and verify the '.'s stop.

Change-Id: I94a82db00076062dbba2c3bc273cbe0731430520
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/463990
Reviewed-by: Scott Collyer <scollyer@chromium.org>

board/cr50/board.c

@@ -345,6 +345,7 @@ static void init_pmu(void)
 void pmu_wakeup_interrupt(void)
 {
 	int exiten, wakeup_src;
+	static int count;
 
 	delay_sleep_by(1 * MSEC);
 
@@ -356,6 +357,16 @@ void pmu_wakeup_interrupt(void)
 	/* Clear pmu reset */
 	GWRITE(PMU, CLRRST, 1);
 
+	/*
+	 * This will print '.' every time cr50 resumes from regular sleep.
+	 * During sleep Cr50 wakes up every half second for HOOK_TICK, so that
+	 * is around the rate cr50 will print '.' while it is idle.
+	 */
+	ccprintf(".");
+	if (!(count % 50))
+		ccprintf("\n");
+	count++;
+
 	if (wakeup_src & GC_PMU_EXITPD_SRC_PIN_PD_EXIT_MASK) {
 		/*
 		 * If any wake pins are edge triggered, the pad logic latches