tipc: simplify link_print by divorcing it from using tipc_printf

To pave the way for a pending cleanup of tipc_printf, and
removal of struct print_buf entirely, we make that task simpler
by converting link_print to issue its messages with standard
printk infrastructure.  [Original idea separated from a larger
patch from Erik Hugne <erik.hugne@ericsson.com>]

Cc: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>