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/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig b/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
index 756e072..a8288e9 100644
--- a/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
+++ b/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
@@ -87,6 +87,7 @@
 CONFIG_PCIE_LAYERSCAPE_RC=y
 CONFIG_U_QE=y
 CONFIG_SYS_QE_FW_ADDR=0x940000
+CONFIG_SCSI_AHCI_PLAT=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y