cmd: CONFIG_CMD_SCSI depends on CONFIG_SCSI

Compiling with CONFIG_CMD_SCSI=y, CONFIG_SCSI results in

    cmd/scsi.c:46: undefined reference to `scsi_scan'

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index bab35fc..091a0ee 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1446,7 +1446,8 @@
 
 config CMD_SCSI
 	bool "scsi - Access to SCSI devices"
-	default y if SCSI
+	depends on SCSI
+	default y
 	help
 	  This provides a 'scsi' command which provides access to SCSI (Small
 	  Computer System Interface) devices. The command provides a way to