[SCSI] aic7xxx: remove separate target and device allocations

Since the aic driver is now taught to speak in terms of the generic
linux devices, we can now also dispense with the transport class get
routines (since we update the parameters when the driver sees they
change) and also plumb it into the spi transport transfer agreement
reporting infrastructure.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>