nfsd4: separate delegreturn case from preprocess_stateid_op

Delegreturn is enough a special case for preprocess_stateid_op to
warrant just open-coding it in delegreturn.

There should be no change in behavior here; we're just reshuffling code.

Thanks to Yang Hongyang for catching a critical typo.

Reviewed-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

include/linux/nfsd/state.h

@@ -263,7 +263,6 @@ struct nfs4_stateid {
 #define RD_STATE	        0x00000010
 #define WR_STATE	        0x00000020
 #define CLOSE_STATE             0x00000040
-#define DELEG_RET               0x00000080
 
 #define seqid_mutating_err(err)                       \
 	(((err) != nfserr_stale_clientid) &&    \