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/include/linux/libata.h b/include/linux/libata.h
index a8ecaaa..a2458df 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -427,9 +427,6 @@
 
 	unsigned int		pad_len;
 
-	unsigned int		nsect;
-	unsigned int		cursect;
-
 	unsigned int		nbytes;
 	unsigned int		curbytes;
 
@@ -1145,8 +1142,7 @@
 	qc->dma_dir = DMA_NONE;
 	qc->__sg = NULL;
 	qc->flags = 0;
-	qc->cursect = qc->cursg = qc->cursg_ofs = 0;
-	qc->nsect = 0;
+	qc->cursg = qc->cursg_ofs = 0;
 	qc->nbytes = qc->curbytes = 0;
 	qc->n_elem = 0;
 	qc->err_mask = 0;