Imx6 new emmc

Due to an EOL on the older Micron MTFC4GMDEA-4M IT part, the replacement Micron MTFC4GACAJCN-4M IT has been qualified for use on this board. This new eMMC flash includes write reliability enabled by default. This will improve reliability for power loss events without requiring user intervention. These modes are further detailed in the eMMC section.

This may require a change to production processes for those who were manually set write reliability and enhanced area for the previous chip. The enh_area and write_reliability settings are permanent and these partition settings are locked once any of them are set. This led to scripts verifying write reliability was set and assuming both were set. The eMMC section includes an example shell script for enabling atomic writes on both versions of this chip.