net: dsa: use capital "OR" for multiple licenses in SPDX

Documentation/process/license-rules.rst and checkpatch expect the SPDX
identifier syntax for multiple licenses to use capital "OR".  Correct it
to keep consistent format and avoid copy-paste issues.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: FLorian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20230823085632.116725-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>