MAINTAINERS: add Conor as a dt-bindings maintainer

Rob asked if I would be interested in helping with the dt-bindings
maintenance, and since I am a glutton for punishment I accepted.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230504-renderer-alive-1c01d431b2a7@spud
Signed-off-by: Rob Herring <robh@kernel.org>

MAINTAINERS

@@ -15608,6 +15608,7 @@ K:	of_overlay_remove
 OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS
 M:	Rob Herring <robh+dt@kernel.org>
 M:	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
+M:	Conor Dooley <conor+dt@kernel.org>
 L:	devicetree@vger.kernel.org
 S:	Maintained
 C:	irc://irc.libera.chat/devicetree