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>

drivers/media/common/saa7146_core.c

@@ -118,8 +118,7 @@ static struct scatterlist* vmalloc_to_sg(unsigned char *virt, int nr_pages)
 		if (NULL == pg)
 			goto err;
 		BUG_ON(PageHighMem(pg));
-		sg_set_page(&sglist[i], pg);
-		sglist[i].length = PAGE_SIZE;
+		sg_set_page(&sglist[i], pg, PAGE_SIZE, 0);
 	}
 	return sglist;