linux-user: do not warn for missing pselect6

Libc will fallback gracefully if pselect6 is not available. Thus put
pselect6 to nowarn until the atomicity issues of the original pselect6
patch are dealt with.
Signed-off-by: NRiku Voipio <riku.voipio@nokia.com>
Cc: Michael Casadevall <mcasadevall@ubuntu.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

linux-user/syscall.c

@@ -5267,6 +5267,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
             ret = do_select(nsel, inp, outp, exp, tvp);
         }
         break;
+#endif
+#ifdef TARGET_NR_pselect6
+    case TARGET_NR_pselect6:
+	    goto unimplemented_nowarn;
 #endif
     case TARGET_NR_symlink:
         {