NFS: Fix size of NFSACL SETACL operations

commit d683cc49daf7c5afca8cd9654aaa1bf63cdf2ad9 upstream.

When encoding the NFSACL SETACL operation, reserve just the estimated
size of the ACL rather than a fixed maximum. This eliminates needless
zero padding on the wire that the server ignores.

Fixes: ee5dc773 ('NFS: Fix "kernel BUG at fs/nfs/nfs3xdr.c:1338!"')
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>