cmd: bdinfo: enable -e when CONFIG_CMD_NET_LWIP=y

Support "bdinfo -e" when lwIP is selected.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>