NFSD: Remove unused nfsd4_compoundargs::cachetype field

This field was added by commit 1091006c ("nfsd: turn on reply
cache for NFSv4") but was never put to use.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/xdr4.h

@@ -724,7 +724,6 @@ struct nfsd4_compoundargs {
 	u32				opcnt;
 	struct nfsd4_op			*ops;
 	struct nfsd4_op			iops[8];
-	int				cachetype;
 };
 
 struct nfsd4_compoundres {