Correct SPL uses of CMD_USB

This converts 8 usages of this option to the non-SPL form, since there is
no SPL_CMD_USB defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/imx8mm-cl-iot-gate.h b/include/configs/imx8mm-cl-iot-gate.h
index 1bb9a91..09d87cf 100644
--- a/include/configs/imx8mm-cl-iot-gate.h
+++ b/include/configs/imx8mm-cl-iot-gate.h
@@ -38,7 +38,7 @@
 # define BOOT_TARGET_MMC(func)
 #endif
 
-#if CONFIG_IS_ENABLED(CMD_USB)
+#if IS_ENABLED(CONFIG_CMD_USB)
 # define BOOT_TARGET_USB(func) func(USB, usb, 0)
 #else
 # define BOOT_TARGET_USB(func)