nfsd: Remove duplicate macro define for max sec label length

NFS4_MAXLABELLEN has defined for sec label max length, use it directly.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --cc fs/nfsd/nfs4proc.c
Simple merge

diff --cc fs/nfsd/nfs4xdr.c
Simple merge

diff --cc fs/nfsd/xdr4.h
Simple merge