hpsa: factor out hpsa_init_cmd function

Factor out hpsa_cmd_init from cmd_alloc().  We also need
this for resubmitting commands down the default RAID path
when they have returned from the ioaccel paths with errors.

In particular, reinitialize the cmd_type and busaddr fields as these
will not be correct for submitting down the RAID stack path
after ioaccel command completion.

This saves time when submitting commands.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Reviewed-by: Hannes Reinecke <hare@Suse.de>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>