libata: kill qc->nsect and cursect

libata used two separate sets of variables to record request size and
current offset for ATA and ATAPI.  This is confusing and fragile.
This patch replaces qc->nsect/cursect with qc->nbytes/curbytes and
kills them.  Also, ata_pio_sector() is updated to use bytes for
qc->cursg_ofs instead of sectors.  The field used to be used in bytes
for ATAPI and in sectors for ATA.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 7484358..52c85af 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1443,15 +1443,10 @@
 		};
 		struct ata_queued_cmd *qc = __ata_qc_from_tag(ap, tag);
 		struct ata_taskfile *cmd = &qc->tf, *res = &qc->result_tf;
-		unsigned int nbytes;
 
 		if (!(qc->flags & ATA_QCFLAG_FAILED) || !qc->err_mask)
 			continue;
 
-		nbytes = qc->nbytes;
-		if (!nbytes)
-			nbytes = qc->nsect << 9;
-
 		ata_dev_printk(qc->dev, KERN_ERR,
 			"cmd %02x/%02x:%02x:%02x:%02x:%02x/%02x:%02x:%02x:%02x:%02x/%02x "
 			"tag %d cdb 0x%x data %u %s\n         "
@@ -1461,7 +1456,7 @@
 			cmd->lbal, cmd->lbam, cmd->lbah,
 			cmd->hob_feature, cmd->hob_nsect,
 			cmd->hob_lbal, cmd->hob_lbam, cmd->hob_lbah,
-			cmd->device, qc->tag, qc->cdb[0], nbytes,
+			cmd->device, qc->tag, qc->cdb[0], qc->nbytes,
 			dma_str[qc->dma_dir],
 			res->command, res->feature, res->nsect,
 			res->lbal, res->lbam, res->lbah,