nfsd: Fix NFSD trace points

nfsd-1915  [003] 77915.780959: write_opened:
	[FAILED TO PARSE] xid=3286130958 fh=0 offset=154624 len=1
nfsd-1915  [003] 77915.780960: write_io_done:
	[FAILED TO PARSE] xid=3286130958 fh=0 offset=154624 len=1
nfsd-1915  [003] 77915.780964: write_done:
	[FAILED TO PARSE] xid=3286130958 fh=0 offset=154624 len=1

Byte swapping and knfsd_fh_hash() are not available in "trace-cmd
report", where the print format string is actually used. These
data transformations have to be done during the TP_fast_assign step.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>