[SCSI] qla2xxx: Code changes for qla data structure refactoring

Following changes have been made:

1. Outstanding commands are based on a request queue, scsi_qla_host
   does not maintain it anymore.

2. start_scsi is accessed via isp_ops struct instead of direct
   invocation.

3. Interrupt registrations are done using response queue instead of
   device id.

Signed-off-by: Anirban Chakraborty <anirban.chakraborty@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>