* Copy a user.txt and uEnv.txt if they exist in /boot in the root fs to the boot partition,
When the user button is pressed, U-boot chooses between these 2 files, user.txt is used
for flashing while uEnv.txt is for a regular boot
* For SD Card image builds, also make a ubi image and copy it to /boot in the root filesystem
This is used by the flashing script to ubiformat the NAND
Signed-off-by: Joel A Fernandes <agnel.joel@gmail.com>