SUNRPC: Update the spkm3 code to use the make_checksum interface

 Also update the tokenlen calculations to accomodate g_token_size().

Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>