drivers/net: wan/dscc4: Remove unused timer

This removes an entirely unused timer, which avoids needing to convert it
to timer_setup().

Cc: Francois Romieu <romieu@fr.zoreil.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>