ata: Migrate CONFIG_SCSI_AHCI to Kconfig

And use 'imply' liberally.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
diff --git a/arch/x86/cpu/baytrail/Kconfig b/arch/x86/cpu/baytrail/Kconfig
index 1d876b1..f47beda 100644
--- a/arch/x86/cpu/baytrail/Kconfig
+++ b/arch/x86/cpu/baytrail/Kconfig
@@ -19,6 +19,7 @@
 	imply MMC_SDHCI
 	imply MMC_SDHCI_SDMA
 	imply SCSI
+	imply SCSI_AHCI
 	imply SPI_FLASH
 	imply SYS_NS16550
 	imply USB