Makefile: allow dm_mmc without of_control

Allow for CONFIG_DM_MMC with platform data rather than
CONFIG_OF_CONTROL.

Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
diff --git a/Makefile b/Makefile
index 37964a8..3525ab3 100644
--- a/Makefile
+++ b/Makefile
@@ -1025,7 +1025,7 @@
 	@echo >&2 "===================================================="
 endif
 ifeq ($(CONFIG_MMC),y)
-ifneq ($(CONFIG_DM_MMC)$(CONFIG_OF_CONTROL)$(CONFIG_BLK),yyy)
+ifneq ($(CONFIG_DM_MMC)$(CONFIG_BLK),yy)
 	@echo >&2 "===================== WARNING ======================"
 	@echo >&2 "This board does not use CONFIG_DM_MMC. Please update"
 	@echo >&2 "the board to use CONFIG_DM_MMC before the v2019.04 release."