NFS: Fix NFSv4 symbolic trace point output

These symbolic values were not being displayed in string form.
TRACE_DEFINE_ENUM was missing in many cases. It also turns out that
__print_symbolic wants an unsigned long in the first field...

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>