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/sandbox64_defconfig b/configs/sandbox64_defconfig
index e1aac61..d82c180 100644
--- a/configs/sandbox64_defconfig
+++ b/configs/sandbox64_defconfig
@@ -104,6 +104,7 @@
 CONFIG_DEBUG_DEVRES=y
 CONFIG_ADC=y
 CONFIG_ADC_SANDBOX=y
+CONFIG_SYS_SATA_MAX_DEVICE=2
 CONFIG_AXI=y
 CONFIG_AXI_SANDBOX=y
 CONFIG_SYS_IDE_MAXBUS=1