Correct SPL use of CMD_STBOARD

This converts 1 usage of this option to the non-SPL form, since there is
no SPL_CMD_STBOARD defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/st/stm32mp1/stm32mp1.c b/board/st/stm32mp1/stm32mp1.c
index 47b3d1b..b0dfa2b 100644
--- a/board/st/stm32mp1/stm32mp1.c
+++ b/board/st/stm32mp1/stm32mp1.c
@@ -129,7 +129,7 @@
 		 fdt_compat && fdt_compat_len ? fdt_compat : "");
 
 	/* display the STMicroelectronics board identification */
-	if (CONFIG_IS_ENABLED(CMD_STBOARD)) {
+	if (IS_ENABLED(CONFIG_CMD_STBOARD)) {
 		ret = uclass_get_device_by_driver(UCLASS_MISC,
 						  DM_DRIVER_GET(stm32mp_bsec),
 						  &dev);