net: lwip: Enable https:// support for wget

net: lwip: Enable https:// support for wget

With the recent changes of lwip & mbedTLS we can now download from
https:// urls instead of just http://.
Adjust our wget lwip version parsing to support both URLs.
While at it adjust the default TCP window for QEMU since https seems to
require at least 16384

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>