Added ATA Pass-Through support to CAM

sys/cam/scsi/scsi_all.c:
        - Added scsi_ata_pass_16 method
          Which use ATA Pass-Through to send commands to the attached disk.

sys/cam/scsi/scsi_all.h:
        - Added defines for all missing ATA Pass-Through commands values.

        - Added scsi_ata_pass_16 method.

        - Fixed a comment typo while I'm here

Reviewed by:	mav
Approved by:	pjd (mentor)
MFC after:	2 weeks