net/lwip: update neighbor cache state using target lladdr
net/lwip: update neighbor cache state using target lladdr

This commit is the patch to update neighbor cache state using target
lladdr.
 - as per the RFC 4861, 83.3 Host specification
   I the link-layer address is the same as that already in the cache,
   the cache entry's state remains unchanged.

Change-Id: Ife813c0b5bded3e4c13308fc444e0c34590f5564
Signed-off-by: Changsoon Kim <c1120524009612ae00648f6848418e342ca4bc0a@samsung.com>

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