net/lwip: add missing initializer of destination cache
net/lwip: add missing initializer of destination cache

This patch adds missing initializer in destination cache when
handling ICMPv6 redirect message.

Change-Id: I0289b3b7fa304ef291137ba8c0aeecbd5c2e9068
Signed-off-by: Wonsang Ryou <bc48fb2bc21aa3a9d3ccd13729d9fc0f5ca913dd@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT