plat/arm: juno: Use TRNG entropy source for SMCCC TRNG interface

Now that we have a framework for the SMCCC TRNG interface, and the
existing Juno entropy code has been prepared, add the few remaining bits
to implement this interface for the Juno Trusted Entropy Source.

We retire the existing Juno specific RNG interface, and use the generic
one for the stack canary generation.

Change-Id: Ib6a6e5568cb8e0059d71740e2d18d6817b07127d
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/plat/arm/board/juno/juno_stack_protector.c b/plat/arm/board/juno/juno_stack_protector.c
index 8c51f57..3924af8 100644
--- a/plat/arm/board/juno/juno_stack_protector.c
+++ b/plat/arm/board/juno/juno_stack_protector.c
@@ -7,15 +7,14 @@
 #include <arch_helpers.h>
 #include <common/debug.h>
 #include <lib/utils.h>
+#include <plat/common/plat_trng.h>
 #include <platform_def.h>
 
-#include "juno_decl.h"
-
 u_register_t plat_get_stack_protector_canary(void)
 {
 	uint64_t entropy;
 
-	if (!juno_getentropy(&entropy)) {
+	if (!plat_get_entropy(&entropy)) {
 		ERROR("Not enough entropy to initialize canary value\n");
 		panic();
 	}