blackfin: don't open-code force_sigsegv()

... especially since we don't have the right k_sigaction here,
so resetting sa_handler won't work.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/blackfin/kernel/signal.c

@@ -210,9 +210,7 @@ setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t * info,
 	return 0;
 
  give_sigsegv:
-	if (sig == SIGSEGV)
-		ka->sa.sa_handler = SIG_DFL;
-	force_sig(SIGSEGV, current);
+	force_sigsegv(sig, current);
 	return -EFAULT;
 }