tipc: Remove unused link event tracking code

Elimintes prototype link event tracking functionality that has never
been fleshed out and doesn't do anything useful at the current time.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>