feat(lfa): add initial implementation for LFA_ACTIVATE

This patch introduces the overall handling of the LFA_ACTIVATE call,
including input validation and invocation flow.
While this covers the core implementation, per-component-specific
handling will be developed in a separate patch. The respective
component callbacks are invoked as part of this logic.

Change-Id: Ie9d4584fc0c0abc9a9faffed62165b4461efed3a
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/include/services/lfa_svc.h b/include/services/lfa_svc.h
index 26dbb7a..69d549c 100644
--- a/include/services/lfa_svc.h
+++ b/include/services/lfa_svc.h
@@ -57,6 +57,8 @@
 #define LFA_MAY_RESET_CPU_SHIFT			2
 #define LFA_CPU_RENDEZVOUS_OPTIONAL_SHIFT	3
 
+#define LFA_SKIP_CPU_RENDEZVOUS_BIT		BIT(0)
+
 /* List of errors as per the specification */
 enum lfa_retc {
 	LFA_SUCCESS			=  0,