fix: assert condition in ffa_partition_info_get_regs helper

Fix off by one error in assert that caused the assert to fire
prematurely and incorrectly.

Signed-off-by: Raghu Krishnamurthy <raghu.ncstate@gmail.com>
Change-Id: I7df68ce7878d26f102a8aa24ae7a4c4897e513d0
diff --git a/src/api.c b/src/api.c
index 8d51374..9116995 100644
--- a/src/api.c
+++ b/src/api.c
@@ -822,7 +822,7 @@
 		if (uuid_is_null) {
 			api_ffa_pack_uuid(xn_1, xn_2, &partitions[idx].uuid);
 		}
-		assert(arg_idx < ARRAY_SIZE(arg_ptrs));
+		assert(arg_idx <= ARRAY_SIZE(arg_ptrs));
 	}
 
 	return ret;