[MACHINE] Add support of Myon II i.MX8M Mini module
This MR added initial support of Myon II i.MX8MM
- add Yconfig and machine config
- update
imx-boot.bbappendto use pre-compiled ATF binary (bl31.bin) from https://git.seco.com/seco-ne/3rd-party/kuk/imx-mkimage-kuk/
Edited by Dmitry Petrov