tipc: update code comments to reflect new uapi header path

Files tipc.h and tipc_config.h were moved to uapi directory, but
the corresponding comments were not updated at the same time.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>