arm: Shorten the Firmware Update (FWU) process

The watchdog is configured with a default value of 256 seconds in order
to implement the Trusted Board Boot Requirements.

For the FVP and Juno platforms, the FWU process relies on a watchdog
reset. In order to automate the test of FWU, the length of this process
needs to be as short as possible. Instead of waiting for those 4 minutes
to have a reset by the watchdog, tell it to reset immediately.

There are no side effects as the value of the watchdog's load register
resets to 0xFFFFFFFF.

Tested on Juno.

Change-Id: Ib1aea80ceddc18ff1e0813a5b98dd141ba8a3ff2
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/plat/arm/board/juno/juno_err.c b/plat/arm/board/juno/juno_err.c
index 700b96c..961bfda 100644
--- a/plat/arm/board/juno/juno_err.c
+++ b/plat/arm/board/juno/juno_err.c
@@ -7,6 +7,7 @@
 #include <errno.h>
 
 #include <arch_helpers.h>
+#include <drivers/arm/sp805.h>
 #include <plat/arm/common/plat_arm.h>
 #include <plat/common/platform.h>
 #include <platform_def.h>
@@ -21,7 +22,9 @@
 	/* Propagate the err code in the NV-flags register */
 	*flags_ptr = err;
 
-	/* Loop until the watchdog resets the system */
+	/* Setup the watchdog to reset the system as soon as possible */
+	sp805_refresh(ARM_SP805_TWDG_BASE, 1U);
+
 	for (;;)
 		wfi();
 }