Correct SPL uses of CMD_MMC

This converts 6 usages of this option to the non-SPL form, since there is
no SPL_CMD_MMC defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/imx8mp_rsb3720.h b/include/configs/imx8mp_rsb3720.h
index d4ab6a6..e577f60 100644
--- a/include/configs/imx8mp_rsb3720.h
+++ b/include/configs/imx8mp_rsb3720.h
@@ -39,7 +39,7 @@
 
 #endif
 
-#if CONFIG_IS_ENABLED(CMD_MMC)
+#if IS_ENABLED(CONFIG_CMD_MMC)
 # define BOOT_TARGET_MMC(func) \
 	func(MMC, mmc, 2)      \
 	func(MMC, mmc, 1)