tipc: Reduce footprint by un-inlining port list routines

Converts port list inline routines that are more than one line into
standard functions, thereby eliminating a significant amount of
repeated code.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>