lockd: Use xdrgen XDR functions for the NLMv3 NM_LOCK procedure

lockd: Use xdrgen XDR functions for the NLMv3 NM_LOCK procedure

Now that nlmsvc_do_lock() has been introduced to handle both
monitored and non-monitored lock requests, the NLMv3 NM_LOCK
procedure can be converted to use xdrgen-generated XDR
functions. This conversion allows the removal of
__nlmsvc_proc_lock(), a helper function that was previously
shared between the LOCK and NM_LOCK procedures.

Replace the NLMPROC_NM_LOCK entry in the nlmsvc_procedures
array with an entry that uses xdrgen-built XDR decoders and
encoders. The procedure handler is reduced to a thin wrapper
around nlmsvc_do_lock() with the monitored flag set to false.

The pc_argzero=0 choice was justified for the LOCK conversion
and applies unchanged here, since both procedures share the
same nlm_lockargs_wrapper layout and decoder.

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