Only include the stack memory for the caller stack

frame, don't go any further, in RNBRemote::SendStopReplyPacketForThread.

These are the memory pre-fetches in the T05 packet and are
included in every private stop that lldb does.  lldb needs, at most,
the caller stack frame so we're sending more data than needed by
including additional stack memory prefetches in this reply packet.

Once we've stopped for a public stop, we're going to do a jThreadsInfo
which will include the stack memory prefetches for all threads, 
including the one which had the stop reason.

llvm-svn: 242380