ata: Migrate CONFIG_SCSI_AHCI to Kconfig

And use 'imply' liberally.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
diff --git a/configs/bananapi_m1_plus_defconfig b/configs/bananapi_m1_plus_defconfig
index 79ff0aa..efe1545 100644
--- a/configs/bananapi_m1_plus_defconfig
+++ b/configs/bananapi_m1_plus_defconfig
@@ -16,6 +16,7 @@
 # CONFIG_SPL_ISO_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
 CONFIG_NETCONSOLE=y
+CONFIG_SCSI_AHCI=y
 CONFIG_ETH_DESIGNWARE=y
 CONFIG_RGMII=y
 CONFIG_SUN7I_GMAC=y