ahci: qoriq: enable snoopable sata read and write

By default the SATA IP on the qoriq SoCs does not generating
coherent/snoopable transactions.  This patch enable it in the
sata axicc register.
In addition, the dma-coherent property must be set on the
SATA controller nodes.

Signed-off-by: Tang Yuantian <yuantian.tang@nxp.com>
Signed-off-by: Tejun Heo <tj@kernel.org>