dm: MIGRATION: Add migration plan for DM_MMC

Given that at this point the MMC subsystem itself has been migrated
along with a number of subsystem drivers, formalize a deadline for
migration.

Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/Makefile b/Makefile
index 2c607d5..ed9b6a1 100644
--- a/Makefile
+++ b/Makefile
@@ -920,6 +920,16 @@
 	@echo "before sending patches to the mailing list."
 	@echo "===================================================="
 endif
+ifeq ($(CONFIG_MMC),y)
+ifneq ($(CONFIG_DM_MMC)$(CONFIG_OF_CONTROL)$(CONFIG_BLK),yyy)
+	@echo "===================== WARNING ======================"
+	@echo "This board does not use CONFIG_DM_MMC. Please update"
+	@echo "the board to use CONFIG_DM_MMC before the v2019.04 release."
+	@echo "Failure to update by the deadline may result in board removal."
+	@echo "See doc/driver-model/MIGRATION.txt for more info."
+	@echo "===================================================="
+endif
+endif
 	@# Check that this build does not use CONFIG options that we do not
 	@# know about unless they are in Kconfig. All the existing CONFIG
 	@# options are whitelisted, so new ones should not be added.