hpsa: do not attempt to read from a write-only register

commit fec62c36 upstream.

Most smartarrays tolerate it, but a few new ones don't.
Without this change some newer Smart Arrays will lock up
and i/o will grind to a halt.
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/scsi/hpsa.h

@@ -214,7 +214,7 @@ static void SA5_submit_command(struct ctlr_info *h,
 	dev_dbg(&h->pdev->dev, "Sending %x, tag = %x\n", c->busaddr,
 		c->Header.Tag.lower);
 	writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
-	(void) readl(h->vaddr + SA5_REQUEST_PORT_OFFSET);
+	(void) readl(h->vaddr + SA5_SCRATCHPAD_OFFSET);
 	h->commands_outstanding++;
 	if (h->commands_outstanding > h->max_outstanding)
 		h->max_outstanding = h->commands_outstanding;