NFS: Fix a typo in nfs_init_timeout_values()

Specifying a retrans=0 mount parameter to a NFS/TCP mount, is
inadvertently causing the NFS client to rewrite any specified
timeout parameter to the default of 60 seconds.

Fixes: a956beda ("NFS: Allow the mount option retrans=0")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>