Refactor FF-A boot info

Refactor the FF-A boot info related types to prepare for adding the FF-A
v1.1 structures.

Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Change-Id: I03dd0275d367611e6156c4ba47bdbacb62296001
diff --git a/environments/sp/sp_entry.c b/environments/sp/sp_entry.c
index 0a709c2..c9b2510 100644
--- a/environments/sp/sp_entry.c
+++ b/environments/sp/sp_entry.c
@@ -26,5 +26,5 @@
 
 	libc_init();
 
-	sp_main((struct ffa_init_info *)a0);
+	sp_main((union ffa_boot_info *)a0);
 }