[SCSI] remove aic7xxx busyq

The aic7xxx driver has two spurious queues in it's linux glue code: the
busyq which queues incoming commands to the driver and the completeq
which queues finished commands before sending them back to the mid-layer

This patch just removes the busyq and makes the aic finally return the
correct status to get the mid-layer to manage its queueing, so a command
is either committed to the sequencer or returned to the midlayer for
requeue.

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