I want to update system image from SD-card with u-boot running on i.MX6dl. The u-boot is pre programed on eMMC and there are 2 slots for SD-card on the i.MX6dl board. If I boot-up the system from eMMC, could I update the system image(kernel, rootfs, etc.) from SD-card with u-boot running ? If so, how could I do it? are there anything I need to configure in u-boot ?