Convert CONFIG_SCSI to Kconfig

This converts the following to Kconfig:
   CONFIG_SCSI

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/configs/highbank_defconfig b/configs/highbank_defconfig
index 041d048..6f19492 100644
--- a/configs/highbank_defconfig
+++ b/configs/highbank_defconfig
@@ -23,5 +23,6 @@
 CONFIG_ISO_PARTITION=y
 CONFIG_EFI_PARTITION=y
 # CONFIG_PARTITION_UUIDS is not set
+CONFIG_SCSI=y
 # CONFIG_MMC is not set
 CONFIG_OF_LIBFDT=y