ata: Migrate CONFIG_LIBATA to Kconfig

This symbol enables some library code used by various SATA drivers,
so make this a non-user-visible symbol select'ed by the respective
drivers, and let moveconfig handle the rest.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
diff --git a/drivers/ata/Kconfig b/drivers/ata/Kconfig
index 38318b4..43e6626 100644
--- a/drivers/ata/Kconfig
+++ b/drivers/ata/Kconfig
@@ -20,8 +20,14 @@
 
 	  See also CMD_SATA which provides command-line support.
 
+config LIBATA
+	bool
+	help
+	  Select this to build and link the libata helper functions.
+
 config SCSI_AHCI
 	bool "Enable SCSI interface to SATA devices"
+	select LIBATA
 	help
 	  Enable this to allow interfacing SATA devices via the SCSI layer.
 
@@ -54,30 +60,35 @@
 
 config DWC_AHSATA
 	bool "Enable DWC AHSATA driver support"
+	select LIBATA
 	help
 	  Enable this driver to support the DWC AHSATA SATA controller found
 	  in i.MX5 and i.MX6 SoCs.
 
 config FSL_SATA
 	bool "Enable Freescale SATA controller driver support"
+	select LIBATA
 	help
 	  Enable this driver to support the SATA controller found in
 	  some Freescale PowerPC SoCs.
 
 config SATA_MV
 	bool "Enable Marvell SATA controller driver support"
+	select LIBATA
 	help
 	  Enable this driver to support the SATA controller found in
 	  some Marvell SoCs.
 
 config SATA_SIL
 	bool "Enable Silicon Image SIL3131 / SIL3132 / SIL3124 SATA driver support"
+	select LIBATA
 	help
 	  Enable this driver to support the SIL3131, SIL3132 and SIL3124
 	  SATA controllers.
 
 config SATA_SIL3114
 	bool "Enable Silicon Image SIL3114 SATA driver support"
+	select LIBATA
 	help
 	  Enable this driver to support the SIL3114 SATA controllers.