CMSIS-RTOS2: Updated TrustZone Examples startup code to set MSPLIM correctly.

In order to allow MSPLIM to be set at the beginning of the reset handler one need to provide __user_setup_stackheap instead of deprecated __user_initial_stackheap. The latter one temporarily reconfigures the stack pointer which leads to a STKOF usage fault.
diff --git a/ARM.CMSIS.pdsc b/ARM.CMSIS.pdsc
index 20efacb..0336e93 100644
--- a/ARM.CMSIS.pdsc
+++ b/ARM.CMSIS.pdsc
@@ -8,6 +8,10 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
+    <release version="5.0.2-dev6">
+      CMSIS-RTOS2:
+      - Updated ARMv8-M startup code to provide __user_setup_stackheap and setup main stack limit.
+    </release>
     <release version="5.0.2-dev5">
       CMSIS-Core(M):
       - Added MPU Management Functions for CM0+/3/4/7