[libata] sata_fsl: fix the controller operating mode

Configure the FSL SATA controller to the preferred, enterprise mode.

Signed-off-by: Yutaka Ando <r46913@freescale.com>
Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
CC: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>