TFM: Change NS lock functions to weak

Default NS lock functions use mutex to guarantee serialization into secure world.
But this mechanism doesn't support pre-rtos and interrupt-disabled.
This commit changes these functions to weak so that platform can override them to provide another mechanism.
This approach is just what TF-M repository is adopting.

https://review.trustedfirmware.org/c/trusted-firmware-m/+/1460

components/TARGET_PSA/TARGET_TFM/COMPONENT_NSPE/interface/src/tfm_ns_lock_rtx.c

@@ -42,6 +42,7 @@ static const osMutexAttr_t ns_lock_attrib = {
 /**
  * \brief NS world, NS lock based dispatcher
  */
+__attribute__((weak))
 uint32_t tfm_ns_lock_dispatch(veneer_fn fn,
                               uint32_t arg0, uint32_t arg1,
                               uint32_t arg2, uint32_t arg3)
@@ -70,6 +71,7 @@ uint32_t tfm_ns_lock_dispatch(veneer_fn fn,
 /**
  * \brief NS world, Init NS lock
  */
+__attribute__((weak))
 enum tfm_status_e tfm_ns_lock_init()
 {
     if (ns_lock.init == false) {