NFSD: Constify @fh argument of knfsd_fh_hash()

Enable knfsd_fh_hash() to be invoked in functions where the
filehandle pointer is a const.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfsfh.h

@@ -225,15 +225,12 @@ static inline bool fh_fsid_match(struct knfsd_fh *fh1, struct knfsd_fh *fh2)
  * returns a crc32 hash for the filehandle that is compatible with
  * the one displayed by "wireshark".
  */
-
-static inline u32
-knfsd_fh_hash(struct knfsd_fh *fh)
+static inline u32 knfsd_fh_hash(const struct knfsd_fh *fh)
 {
 	return ~crc32_le(0xFFFFFFFF, (unsigned char *)&fh->fh_base, fh->fh_size);
 }
 #else
-static inline u32
-knfsd_fh_hash(struct knfsd_fh *fh)
+static inline u32 knfsd_fh_hash(const struct knfsd_fh *fh)
 {
 	return 0;
 }