linux-user/sparc/signal.c: Remove unnecessary comment

Remove a comment suggesting that we need to call tb_flush()
after writing the SPARC signal frame trampoline insns.
This isn't necessary in QEMU, because (even if the guest
architecture requires explicit icache maintenance) we
ensure that memory writes result in invalidation of
translated code from that memory.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-Id: <20181009184017.15675-1-peter.maydell@linaro.org>
Signed-off-by: NLaurent Vivier <laurent@vivier.eu>

linux-user/sparc/signal.c

@@ -258,10 +258,6 @@ void setup_frame(int sig, struct target_sigaction *ka,
         __put_user(val32, &sf->insns[1]);
         if (err)
             goto sigsegv;
-
-        /* Flush instruction space. */
-        // flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
-        // tb_flush(env);
     }
     unlock_user(sf, sf_addr, sizeof(struct target_signal_frame));
     return;