block: replace end_request() with [__]blk_end_request_cur()

end_request() has been kept around for backward compatibility;
however, it's about time for it to go away.

* There aren't too many users left.

* Its use of @updtodate is pretty confusing.

* In some cases, newer code ends up using mixture of end_request() and
  [__]blk_end_request[_all](), which is way too confusing.

So, add [__]blk_end_request_cur() and replace end_request() with it.
Most conversions are straightforward.  Noteworthy ones are...

* paride/pcd: next_request() updated to take 0/-errno instead of 1/0.

* paride/pf: pf_end_request() and next_request() updated to take
  0/-errno instead of 1/0.

* xd: xd_readwrite() updated to return 0/-errno instead of 1/0.

* mtd/mtd_blkdevs: blktrans_discard_request() updated to return
  0/-errno instead of 1/0.  Unnecessary local variable res
  initialization removed from mtd_blktrans_thread().

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Joerg Dorchain <joerg@dorchain.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Laurent Vivier <Laurent@lvivier.info>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: unsik Kim <donari75@gmail.com>
diff --git a/drivers/block/paride/pcd.c b/drivers/block/paride/pcd.c
index e91d4b4..9fd57c2 100644
--- a/drivers/block/paride/pcd.c
+++ b/drivers/block/paride/pcd.c
@@ -735,16 +735,16 @@
 			ps_set_intr(do_pcd_read, NULL, 0, nice);
 			return;
 		} else
-			end_request(pcd_req, 0);
+			__blk_end_request_cur(pcd_req, -EIO);
 	}
 }
 
-static inline void next_request(int success)
+static inline void next_request(int err)
 {
 	unsigned long saved_flags;
 
 	spin_lock_irqsave(&pcd_lock, saved_flags);
-	end_request(pcd_req, success);
+	__blk_end_request_cur(pcd_req, err);
 	pcd_busy = 0;
 	do_pcd_request(pcd_queue);
 	spin_unlock_irqrestore(&pcd_lock, saved_flags);
@@ -781,7 +781,7 @@
 
 	if (pcd_command(pcd_current, rd_cmd, 2048, "read block")) {
 		pcd_bufblk = -1;
-		next_request(0);
+		next_request(-EIO);
 		return;
 	}
 
@@ -796,7 +796,7 @@
 	pcd_retries = 0;
 	pcd_transfer();
 	if (!pcd_count) {
-		next_request(1);
+		next_request(0);
 		return;
 	}
 
@@ -815,7 +815,7 @@
 			return;
 		}
 		pcd_bufblk = -1;
-		next_request(0);
+		next_request(-EIO);
 		return;
 	}