gdb: fix remote-sim.c build

Commit 183be222907a ("gdb, gdbserver: make target_waitstatus safe")
broke the remote-sim.c build.  In fact, it does some wrong changes,
result of a bad sed invocation.

Fix it by adjusting the code to the new target_waitstatus API.

Change-Id: I3236ff7ef7681fc29215f68be210ff4263760e91
1 file changed