[SCSI] mpt2sas: cleanup interrupt routine and config_request optimization

Cleaned up base_interrupt routine to be more effiecent.

Deleted about a third of the config page API by moving redundant code from all
the calling functions to _config_request.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Reviewed-by: Eric Moore <Eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>