turn SCSI_MLQUEUE_HOST_BUSY when no free request slots
- move scsi_remove_host() to the begin of hpt_remove(), or it will
  not work after resources being released.

Signed-off-by: HighPoint Linux Team <linux@highpoint-tech.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>