net: lwip: add CONFIG_LWIP_DEBUG_RXTX

Add Kconfig symbol LWIP_DEBUG_RXTX to dump the incoming and outgoing
packets when NET_LWIP=y.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
2 files changed