core: Enable DM by default

There are no longer any platforms which do not enable DM, move this to a
def_bool y and remove the check in the Makefile.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 3866cc6..7cdd31f 100644
--- a/Makefile
+++ b/Makefile
@@ -1138,14 +1138,6 @@
 	@echo >&2 "arch-specific scripts with no tests."
 	@echo >&2 "===================================================="
 endif
-ifneq ($(CONFIG_DM),y)
-	@echo >&2 "===================== WARNING ======================"
-	@echo >&2 "This board does not use CONFIG_DM. CONFIG_DM will be"
-	@echo >&2 "compulsory starting with the v2020.01 release."
-	@echo >&2 "Failure to update may result in board removal."
-	@echo >&2 "See doc/develop/driver-model/migration.rst for more info."
-	@echo >&2 "===================================================="
-endif
 	$(call deprecated,CONFIG_WDT,DM watchdog,v2019.10,\
 		$(CONFIG_WATCHDOG)$(CONFIG_HW_WATCHDOG))
 	$(call deprecated,CONFIG_DM_I2C,I2C drivers,v2022.04,$(CONFIG_SYS_I2C_LEGACY))
diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index c9bf5de..0dc442b 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -1,7 +1,7 @@
 menu "Generic Driver Options"
 
 config DM
-	bool "Enable Driver Model"
+	def_bool y
 	help
 	  This config option enables Driver Model. This brings in the core
 	  support, including scanning of platform data on start-up. If