cactus: add exception/interrupt framework

This patch adds following changes to cactus
 1. Set up exception vector base address.
 2. Add skeleton interrupt handler.
 3. Install default tftf cpu exception handler.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I265553918b45a0e7e80ef0d7c48c09abfbec1a5f
diff --git a/spm/cactus/cactus_main.c b/spm/cactus/cactus_main.c
index 5ca206b..0809716 100644
--- a/spm/cactus/cactus_main.c
+++ b/spm/cactus/cactus_main.c
@@ -147,6 +147,13 @@
 	init_xlat_tables();
 }
 
+int tftf_irq_handler_dispatcher(void)
+{
+	ERROR("%s\n", __func__);
+
+	return 0;
+}
+
 void __dead2 cactus_main(void)
 {
 	assert(IS_IN_EL1() != 0);