nfs: Fix fscache stat printing in nfs_show_stats()

nfs_show_stats() was incorrectly reading statistics for bytes when printing that
for fsc. It caused files like /proc/self/mountstats to report incorrect fsc
statistics for NFS mounts.

Signed-off-by: Tuo Chen Peng <tpeng@nvidia.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>