Hi Wolfgang, I do not know of any active efforts to support i.MX6 in coreboot. However, if you are interested in leading the porting effort then we can help. I think that ARM-specific portions will be simple. The hard parts are DRAM and peripheral init. If we can help you boot to the point where UART works, will you feel comfortable doing the remaining work?
As far as I know, the focus of ARM development in coreboot is on Exynos5 (Cortex-A15). We are currently booting Exynos5250 and Exynos5420 systems. TI AM335X (Cortex-A8) support is still somewhat active, but is a side-project. We can initialize the CPU and get serial console output so future development will be much easier.