dt-bindings: Turn on undocumented compatible checks

The undocumented compatibles in the examples are down to just a few left. Turn on the warning by default. The increased visibility should get the remaining warnings fixed.

---
After the last batch of fixes I've sent out, there's 6 warnings remaining:

['socionext,milbeaut-usio-uart'] ['sprd,sc9863a-glbregs', 'syscon', 'simple-mfd'] ['brcm,bcm2711-avs-monitor', 'syscon', 'simple-mfd'] ['fsl,imx6q-anatop', 'syscon', 'simple-mfd'] ['hisilicon,hi3798cv200-combphy'] ['qca,ar9331-switch']

 Documentation/devicetree/bindings/Makefile | 3 ---
 1 file changed, 3 deletions(-)

index 3e886194b043..3e3e49d8a733 100644
@@ -61,9 +61,6 @@ override DTC_FLAGS := \
 	-Wno-unique_unit_address \
 	-Wunique_unit_address_if_enabled
 
-# Disable undocumented compatible checks until warning free
-override DT_CHECKER_FLAGS ?=
-
 $(obj)/processed-schema.json: $(DT_DOCS) $(src)/.yamllint check_dtschema_version FORCE
 	$(call if_changed_rule,chkdt)
 

2.42.0

Yay!

Best regards,
Krzysztof