dt-bindings: update Krzysztof Kozlowski's email

Krzysztof Kozlowski's @canonical.com email stopped working, so switch to
generic @kernel.org account for all Devicetree bindings.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20220330074016.12896-2-krzysztof.kozlowski@linaro.org