[SCSI] aha152x: fix variable use before initialisation and other bugs

- change interface of the reset functions from Scsi_Cmnd to Scsi_Host.
- add functions with the original interface and rename the new
  functions to reflect the new interface.
- call these from the pcmcia driver, thereby avoiding the need to
  construct a (broken) Scsi_Cmnd from a Scsi_Host.
- just run the bh if the interrupt is from the controller and if so
  ensure that it's only called once per interrupt.

Signed-off-by: Juergen E. Fischer <fischer@linux-buechse.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>