MAINTAINERS: Update NetEffect entry

Correct web link as www.neteffect.com is no longer valid.  Remove
Chien Tung as maintainer.  I am moving on to other responsibilities at
Intel.  Thanks for all the fish.

Signed-off-by: Chien Tung <chien.tin.tung@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>