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/fvp/fvp_bl1_setup.c b/plat/arm/board/fvp/fvp_bl1_setup.c
index 420df45..b90ddcd 100644
--- a/plat/arm/board/fvp/fvp_bl1_setup.c
+++ b/plat/arm/board/fvp/fvp_bl1_setup.c
@@ -52,3 +52,12 @@
 	if ((arm_config.flags & ARM_CONFIG_FVP_HAS_SMMUV3) != 0U)
 		smmuv3_security_init(PLAT_FVP_SMMUV3_BASE);
 }
+
+__dead2 void bl1_plat_fwu_done(void *client_cookie, void *reserved)
+{
+	/* Setup the watchdog to reset the system as soon as possible */
+	sp805_refresh(ARM_SP805_TWDG_BASE, 1U);
+
+	while (1)
+		wfi();
+}