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/chromebook_link64_defconfig b/configs/chromebook_link64_defconfig
index febbeb5..8fb4712 100644
--- a/configs/chromebook_link64_defconfig
+++ b/configs/chromebook_link64_defconfig
@@ -57,6 +57,7 @@
 CONFIG_SPL_REGMAP=y
 CONFIG_SYSCON=y
 CONFIG_SPL_SYSCON=y
+CONFIG_SCSI=y
 CONFIG_CPU=y
 CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_INTEL=y