[U-Boot] Add support for imxrt

Hello everybody,

I would like to port imxrt to u-boot and I would like to ask you: - do you have the interest on upstreaming it? if yes: I've seen how they've dealt with 'stm32' and 'stm32mp' that is similar to 'imxrt' and 'imx'. So should follow the same criterias for porting? I mean adding the new folder 'mach-imxrt'?

Also, do I find some of you in IRC sometimes?

Thanks in advance Best regards