net/lwip: change the place of exception handling
net/lwip: change the place of exception handling

Validation of hop limit for NS message is working at the ipv6 header level.
And there's no need to process if it's not valid so it should be
processed ASAP.

Change-Id: I12e4c2216a6964cbc3f4e8b6eaa92d4497b4028d
Signed-off-by: jisuu.kim <800dec47d2987cee7cc3d7aee71bc11b56f5042e@samsung.com>

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