sim,base: Get rid of the system/gdb "breakpoint" methods.

This unused pair of methods could be used to trigger a breakpoint within
the remote GDB stub, but was unused and would need to be called from an
instance of GDB attached to gem5 itself.

The system's version of breakpoint was also limitted in that it would
only cause a breakpoint in the first thread's GDB and no other.

Change-Id: I53ceab78667610177dbb8be1def3a88262befeec
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/44031
Reviewed-by: Boris Shingarov <shingarov@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/remote_gdb.hh

@@ -157,7 +157,6 @@ class BaseRemoteGDB
     void replaceThreadContext(ThreadContext *_tc) { tc = _tc; }
 
     bool trap(int type);
-    bool breakpoint() { return trap(SIGTRAP); }
 
     /** @} */ // end of api_remote_gdb
 

src/sim/system.cc

@@ -300,16 +300,6 @@ System::setMemoryMode(Enums::MemoryMode mode)
     memoryMode = mode;
 }
 
-bool System::breakpoint()
-{
-    if (!threads.size())
-        return false;
-    auto *gdb = threads.thread(0).gdb;
-    if (!gdb)
-        return false;
-    return gdb->breakpoint();
-}
-
 ContextID
 System::registerThreadContext(ThreadContext *tc, ContextID assigned)
 {

src/sim/system.hh

@@ -552,9 +552,6 @@ class System : public SimObject, public PCEventScope
 
     void workItemEnd(uint32_t tid, uint32_t workid);
 
-  public:
-    bool breakpoint();
-
   protected:
     /**
      * Range for memory-mapped m5 pseudo ops. The range will be