SG: Change sg_set_page() to take length and offset argument

Most drivers need to set length and offset as well, so may as well fold
those three lines into one.

Add sg_assign_page() for those two locations that only needed to set
the page, where the offset/length is set outside of the function context.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index ce69b9e..98dfd6e 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -3797,13 +3797,11 @@
 	sg = &(STbp->sg[0]);
 	frp = STbp->frp;
 	for (i=count=0; count < length; i++) {
-		sg_set_page(&sg[i], frp[i].page);
 		if (length - count > frp[i].length)
-			sg[i].length = frp[i].length;
+			sg_set_page(&sg[i], frp[i].page, frp[i].length, 0);
 		else
-			sg[i].length = length - count;
+			sg_set_page(&sg[i], frp[i].page, length - count, 0);
 		count += sg[i].length;
-		sg[i].offset = 0;
 	}
 	STbp->sg_segs = i;
 	STbp->frp_sg_current = length;
@@ -4446,15 +4444,13 @@
         }
 
 	/* Populate the scatter/gather list */
-	sg_set_page(&sgl[0], pages[0]);
-	sgl[0].offset = uaddr & ~PAGE_MASK;
+	sg_set_page(&sgl[0], pages[0], 0, uaddr & ~PAGE_MASK);
 	if (nr_pages > 1) {
 		sgl[0].length = PAGE_SIZE - sgl[0].offset;
 		count -= sgl[0].length;
 		for (i=1; i < nr_pages ; i++) {
-			sg_set_page(&sgl[i], pages[i]);;
-			sgl[i].offset = 0;
-			sgl[i].length = count < PAGE_SIZE ? count : PAGE_SIZE;
+			sg_set_page(&sgl[i], pages[i],
+				    count < PAGE_SIZE ? count : PAGE_SIZE, 0);;
 			count -= PAGE_SIZE;
 		}
 	}