MAINTAINERS: Change FSL DDR EDAC maintainership

Last email from York Sun is from 2019, so move him to Credits.  Frank Li
volunteered to keep maintaining the driver, add him as a reviewer for now.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20241003193348.102234-1-krzysztof.kozlowski@linaro.org