lightnvm: move rq->error to nvm_rq->error

Instead of passing request error into the LightNVM modules, incorporate
it into the nvm_rq.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index a83298f..9acc71a 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -149,7 +149,7 @@
 };
 
 struct nvm_rq;
-typedef void (nvm_end_io_fn)(struct nvm_rq *, int);
+typedef void (nvm_end_io_fn)(struct nvm_rq *);
 
 struct nvm_rq {
 	struct nvm_tgt_instance *ins;
@@ -173,6 +173,8 @@
 	uint8_t opcode;
 	uint16_t nr_pages;
 	uint16_t flags;
+
+	int error;
 };
 
 static inline struct nvm_rq *nvm_rq_from_pdu(void *pdu)