ATA: Add FSL sata v2 controller support

In FSL sata v2 block, the snoop bit of PRDT Word3 description
information is at bit28 instead of bit22.

This patch adds FSL sata v2 probe and resolve this difference.

Signed-off-by: Lei Xu <B33228@freescale.com>
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Acked-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>