Makefile: Use common code for MMC deprecation warning

Update the MMC check to use the 'deprecated' function.

Tested with zc5202

Old message:

===================== WARNING ======================
This board does not use CONFIG_DM_MMC. Please update
the board to use CONFIG_DM_MMC before the v2019.04 release.
Failure to update by the deadline may result in board removal.
See doc/driver-model/migration.rst for more info.
====================================================

New message:

===================== WARNING ======================
This board does not use CONFIG_DM_MMC (Driver Model
for MMC). Please update the board to use
CONFIG_DM_MMC before the v2019.04 release. Failure to
update by the deadline may result in board removal.
See doc/driver-model/migration.rst for more info.
====================================================
Signed-off-by: NSimon Glass <sjg@chromium.org>

Makefile

@@ -1087,16 +1087,7 @@ ifneq ($(CONFIG_DM),y)
 	@echo >&2 "See doc/driver-model/migration.rst for more info."
 	@echo >&2 "===================================================="
 endif
-ifeq ($(CONFIG_MMC),y)
-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."
-	@echo >&2 "Failure to update by the deadline may result in board removal."
-	@echo >&2 "See doc/driver-model/migration.rst for more info."
-	@echo >&2 "===================================================="
-endif
-endif
+	$(call deprecated,CONFIG_DM_MMC CONFIG_BLK,MMC,v2019.04,$(CONFIG_MMC))
 ifeq ($(CONFIG_USB),y)
 ifneq ($(CONFIG_DM_USB)$(CONFIG_OF_CONTROL)$(CONFIG_BLK),yyy)
 	@echo >&2 "===================== WARNING ======================"