In the ICall_leaveCSImpl(ICall_CSState key) and ICall_CSState ICall_enterCSImpl(void)

When we enter CS, we disable Swi first, but the hwi can still occur before we disable hwi. Most of the times, there is no issue.

However, in some use cases, it is possible that sometimes the radio runs right after Swi is disabled, which then can eventually causing the wrong keys being used when we exist CS causing Swi being disable forever.

The proposed fix is that to disable hwi first when entering CS to make sure nothing can run.
And to enable hwi last when exiting CS.

ICall_CSState ICall_enterCSImpl(void)
{

  ICall_CSStateUnion cu;
  cu.each.hwikey = (uint_least16_t) Hwi_disable();
  cu.each.swikey = (uint_least16_t) Swi_disable();
  return cu.state;
}

/* leave critical section implementation. See header file for comment */
void ICall_leaveCSImpl(ICall_CSState key)
{
  ICall_CSStateUnion *cu = (ICall_CSStateUnion *) &key;
  Swi_restore((uint32_t) cu->each.swikey);
  Hwi_restore((uint32_t) cu->each.hwikey);
}