linux-user: Remove the unused "not implemented" signal handling stubs

Now we've dropped unicore32, all of the architectures we support
for linux-user implement the signal handling routines. The
dummy "just print a message" versions are unimplemented, so we
can drop them entirely.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20180308144733.25615-3-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/signal.c

@@ -6772,32 +6772,7 @@ long do_rt_sigreturn(CPUArchState *env)
 }
 
 #else
-
-static void setup_frame(int sig, struct target_sigaction *ka,
-                        target_sigset_t *set, CPUArchState *env)
-{
-    fprintf(stderr, "setup_frame: not implemented\n");
-}
-
-static void setup_rt_frame(int sig, struct target_sigaction *ka,
-                           target_siginfo_t *info,
-                           target_sigset_t *set, CPUArchState *env)
-{
-    fprintf(stderr, "setup_rt_frame: not implemented\n");
-}
-
-long do_sigreturn(CPUArchState *env)
-{
-    fprintf(stderr, "do_sigreturn: not implemented\n");
-    return -TARGET_ENOSYS;
-}
-
-long do_rt_sigreturn(CPUArchState *env)
-{
-    fprintf(stderr, "do_rt_sigreturn: not implemented\n");
-    return -TARGET_ENOSYS;
-}
-
+#error Target needs to add support for signal handling
 #endif
 
 static void handle_pending_signal(CPUArchState *cpu_env, int sig,