ata: Migrate CONFIG_FSL_SATA to Kconfig

Use 'imply' here liberally to avoid the combinatorial explosion of
defconfig changes in the PowerPC boards.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
diff --git a/drivers/ata/Kconfig b/drivers/ata/Kconfig
index 8dfa467..2eab570 100644
--- a/drivers/ata/Kconfig
+++ b/drivers/ata/Kconfig
@@ -47,6 +47,12 @@
 	  Enable this driver to support Sata devices through
 	  Synopsys DWC AHCI module.
 
+config FSL_SATA
+	bool "Enable Freescale SATA controller driver support"
+	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"
 	help