refactor: move `inc/hf/arch/plat/ffa` to `inc/hf/ffa`

Change-Id: I05c2cd1aa3753cd60021015c4582831eb03db3c9
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/inc/hf/manifest.h b/inc/hf/manifest.h
index 40fa307e..eac1e1b 100644
--- a/inc/hf/manifest.h
+++ b/inc/hf/manifest.h
@@ -14,6 +14,7 @@
 #include "hf/ffa.h"
 #include "hf/ffa_partition_manifest.h"
 #include "hf/memiter.h"
+#include "hf/static_assert.h"
 #include "hf/string.h"
 #include "hf/vm.h"