tipc: Simplify enforcement of reserved name type prohibition

Streamlines the logic that prevents an application from binding a
reserved TIPC name type to a port by moving the check to the code
that handles a socket bind() operation. This allows internal TIPC
subsystems to bind a reserved name without having to set an atomic
flag to gain permission to use such a name. (This simplification is
now possible due to the elimination of support for TIPC's native API.)

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