[POWERPC] Fix viodasd driver with scatterlist debug

The iSeries viodasd drivers does some very strange things with
scatterlists, one of these causing a BUG_ON to trigger when
scatterlist debugging is enabled due to initializing the
scatterlist with memset instead of sg_init_table().

This fixes it by using sg_init_table().  The rest of the stuff
it does to that poor list is still pretty awful but it will work.

I may look into fixing things in a nicer way some other time.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

drivers/block/viodasd.c

@@ -528,8 +528,7 @@ static int block_event_to_scatterlist(const struct vioblocklpevent *bevent,
 		numsg = VIOMAXBLOCKDMA;
 
 	*total_len = 0;
-	memset(sg, 0, sizeof(sg[0]) * VIOMAXBLOCKDMA);
-
+	sg_init_table(sg, VIOMAXBLOCKDMA);
 	for (i = 0; (i < numsg) && (rw_data->dma_info[i].len > 0); ++i) {
 		sg_dma_address(&sg[i]) = rw_data->dma_info[i].token;
 		sg_dma_len(&sg[i]) = rw_data->dma_info[i].len;