Hi,

In ESP SCSI adapter, IRQ line state should always be in sync with the 
STAT_INT bit. This patch enforces this, by creating functions to raise 
or lower the irq level.
This fixes bugs in do_cmd(), write_response(), esp_mem_readb(), 
esp_mem_writeb(), where it was not handled properly.
Also adds IRQ line deassertion at reset.
Finally, rename STAT_IN to STAT_INT, according to datasheet.

Hervé