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>
diff --git a/drivers/ata/Kconfig b/drivers/ata/Kconfig
index 57121f6..fe589d3 100644
--- a/drivers/ata/Kconfig
+++ b/drivers/ata/Kconfig
@@ -110,6 +110,7 @@
 config SATA_SIL
 	bool "Enable Silicon Image SIL3131 / SIL3132 / SIL3124 SATA driver support"
 	select LIBATA
+	select AHCI if BLK
 	help
 	  Enable this driver to support the SIL3131, SIL3132 and SIL3124
 	  SATA controllers.