FEXCore: Have the Syscall IR op jump to the dispatcher

Have it treated as a block terminator IR and instead of doing
syscall+exitfunction, just do syscall and jump in to the dispatcher.

This is necessary for code invalidation and reuse for code that is stuck
in long running syscalls. We'll need to do something similar for thunks
later, although the recursive nature of thunk+callback can make that a
little squirrely.

FEXCore/Source/Interface/Core/OpcodeDispatcher.cpp

@@ -59,12 +59,6 @@ void OpDispatchBuilder::SyscallOp(OpcodeArgs, bool IsSyscallInst) {
 
   FlushRegisterCache();
   _Syscall();
-
-  if (Op->TableInfo->Flags & X86Tables::InstFlags::FLAGS_BLOCK_END) {
-    // RIP could have been updated after coming back from the Syscall.
-    NewRIP = _LoadContextGPR(GPRSize, offsetof(FEXCore::Core::CPUState, rip));
-    ExitFunction(NewRIP);
-  }
 }
 
 void OpDispatchBuilder::ThunkOp(OpcodeArgs) {