Convert CONFIG_SCSI_AHCI_PLAT et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SCSI_AHCI_PLAT
   CONFIG_SYS_SCSI_MAX_SCSI_ID
   CONFIG_SYS_SCSI_MAX_LUN
   CONFIG_SYS_SATA_MAX_DEVICE

Drop CONFIG_SCSI for everything except the sandbox build. We only need
one build for tests.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/highbank_defconfig b/configs/highbank_defconfig
index 3e8bfcf..61a25c2 100644
--- a/configs/highbank_defconfig
+++ b/configs/highbank_defconfig
@@ -29,3 +29,5 @@
 # CONFIG_MMC is not set
 CONFIG_CALXEDA_XGMAC=y
 CONFIG_SCSI=y
+CONFIG_SCSI_AHCI_PLAT=y
+CONFIG_SYS_SCSI_MAX_SCSI_ID=5