i2c: Fix the migration warning

While there is a CONFIG_I2C it does not really mean anything and is
defined by only a few dozen boards. This should key off
CONFIG_SYS_I2C_LEGACY instead.

Fix it.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NHeiko Schocher <hs@denx.de>

Makefile

@@ -1128,7 +1128,7 @@ endif
 	$(call deprecated,CONFIG_WDT,DM watchdog,v2019.10,\
 		$(CONFIG_WATCHDOG)$(CONFIG_HW_WATCHDOG))
 	$(call deprecated,CONFIG_DM_ETH,Ethernet drivers,v2020.07,$(CONFIG_NET))
-	$(call deprecated,CONFIG_DM_I2C,I2C drivers,v2022.04,$(CONFIG_I2C))
+	$(call deprecated,CONFIG_DM_I2C,I2C drivers,v2022.04,$(CONFIG_SYS_I2C_LEGACY))
 	@# 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.