TF-M patch: Fix tfm_ns_lock_init issue (TF-M issue #239)

- Link to bug tracking: https://developer.trustedfirmware.org/T239

(cherry picked from commit 5f2e4b3)

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

@@ -6,9 +6,9 @@
  */
 #include <stdint.h>
 #include <stdbool.h>
-
+#include "cmsis.h"
+#include "rtx_os.h"
 #include "cmsis_os2.h"
-
 #include "tfm_api.h"
 #include "tfm_ns_lock.h"
 
@@ -29,11 +29,14 @@ static struct ns_lock_state ns_lock = {.init=false, .id=NULL};
 /**
  * \brief Mutex properties, NS lock
  */
+
+static osRtxMutex_t ns_lock_cb = { 0 };
+
 static const osMutexAttr_t ns_lock_attrib = {
     .name = "ns_lock",
     .attr_bits = osMutexPrioInherit,
-    .cb_mem = NULL,
-    .cb_size = 0U
+    .cb_mem = &ns_lock_cb,
+    .cb_size = sizeof(ns_lock_cb)
 };
 
 /**