[SCSI] hpsa: do readl after writel in main i/o path to ensure commands don't get lost.

Apparently we've been doin it rong for a decade, but only lately do we
run into problems.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <jbottomley@parallels.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/hpsa.h

@@ -212,6 +212,7 @@ 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);
 	h->commands_outstanding++;
 	if (h->commands_outstanding > h->max_outstanding)
 		h->max_outstanding = h->commands_outstanding;