SPM: Fix warning of variable length data

Fix the warnings from armclang of variable length data not placed
at the end of struct.

Change-Id: I39cdb66b9f20691fa937334a5fc8ac4af9a92e9a
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
diff --git a/secure_fw/include/load/partition_defs.h b/secure_fw/include/load/partition_defs.h
index 014f833..74d04d0 100644
--- a/secure_fw/include/load/partition_defs.h
+++ b/secure_fw/include/load/partition_defs.h
@@ -36,7 +36,12 @@
 #define SPM_PART_FLAG_PSA_ROT                   (1U << 8)
 #define SPM_PART_FLAG_IPC                       (1U << 9)
 
-/* Common partition structure type */
+/*
+ * Common partition structure type, the extendable data is right after it.
+ * Extendable data has different size for each partition, and must be 4-byte
+ * aligned. It includes: stack and heap position, dependencies, services and
+ * assets data.
+ */
 struct partition_static_info_t {
     uint32_t        psa_ff_ver;         /* Encode the version with magic    */
     uint32_t        pid;                /* Partition ID                     */
@@ -47,7 +52,6 @@
     uint32_t        ndeps;              /* Dependency number                */
     uint32_t        nservices;          /* Service number                   */
     uint32_t        nassets;            /* Asset numbers                    */
-    uintptr_t       vars[];             /* Struct extendable indicator      */
 } __attribute__((aligned(4)));
 
 #endif /* __PARTITION_DEFS_H__ */