esp_scsi: read status registers

A read to ESP_INTRPT will clear ESP_STATUS and ESP_SSTEP. So read
all status registers in one go to avoid losing information.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>