lockd: Simplify cast_status() in svcproc.c

lockd: Simplify cast_status() in svcproc.c

Clean up: The svcproc.c file handles only NLM v1 and v3 requests.
NLMv4 requests are routed to a separate procedure table in
svc4proc.c, so rqstp->rq_vers can never be 4 in this context.

Remove the unused vers parameter and the dead "vers != 4" check from
cast_to_nlm(). This eliminates the need for the macro wrapper.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>