refactor(ff-a): init

Move `plat_ffa_init` and `plat_ffa_log_init` to new `init.c` file.

Change-Id: I65484c6d5cd868de01c5bb8fb3edd103a0d61262
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/src/ffa/hypervisor/indirect_messaging.c b/src/ffa/hypervisor/indirect_messaging.c
index c1da53f..a1a5d4a 100644
--- a/src/ffa/hypervisor/indirect_messaging.c
+++ b/src/ffa/hypervisor/indirect_messaging.c
@@ -11,6 +11,7 @@
 #include "hf/arch/other_world.h"
 
 #include "hf/api.h"
+#include "hf/ffa/init.h"
 #include "hf/ffa_internal.h"
 #include "hf/vm.h"