linux-user: Don't omit comma for strace of rt_sigaction()

Pass the 'last' parameter of print_signal() through to
print_raw_param(); this fixes a problem where we weren't printing
the comma separator for strace of rt_sigaction() when the signal
was an unnamed (ie realtime) one:
  6856 rt_sigaction(230xf6fff870,0xf6fff8fc) = 0

Signed-off-by: Peter Maydell <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>

Author: pm215

Diff for: linux-user/strace.c

@@ -143,7 +143,7 @@ print_signal(abi_ulong arg, int last)
     case TARGET_SIGTTOU: signal_name = "SIGTTOU"; break;
     }
     if (signal_name == NULL) {
-        print_raw_param("%ld", arg, 1);
+        print_raw_param("%ld", arg, last);
         return;
     }
     gemu_log("%s%s", signal_name, get_comma(last));