SUNRPC: fix build-warning due to format missmatch

fix build-warning introduced by commit: f0eede10 ("SUNRPC: use
jiffies_to_msecs for converting jiffies") which did not fixup
the format properly (my bad).

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>