ata: sata_sil: Add DM support for Silicon sata driver

Add DM support for Silicon(SIL3131 / SIL3132 / SIL3124) sata driver as
few of the PowerPC platforms such as P series based boards need to
use SATA_SIL with DM,

Also fix below warning while PowerPC P series boards compilation,

===================== WARNING ======================"
This board does use CONFIG_LIBATA but has CONFIG_AHCI not"
enabled. Please update the storage controller driver to use"
CONFIG_AHCI before the v2019.07 release."
Failure to update by the deadline may result in board removal."
See doc/driver-model/MIGRATION.txt for more info."
===================================================="

Signed-off-by: Peng Ma <peng.ma@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>