tun.c on WIN32: remove more unused variables

tun.c on WIN32: remove more unused variables

Fixes:
  tun.c: In function ‘do_ifconfig_ipv4’:
  tun.c:1217:17: warning: variable ‘ifconfig_remote_netmask’ set but not
  used [-Wunused-but-set-variable]
     const char *ifconfig_remote_netmask = NULL;

  tun.c:1213:10: warning: unused variable ‘tun’ [-Wunused-variable]
     bool tun = is_tun_p2p(tt);

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20210403172403.9452-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22019.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>