fastboot: add support for continue command
The fastboot continue command is defined to exit fastboot and continue
autoboot. This commit implements the continue command and the exiting of
fastboot only. Subsequent u-boot commands can be processed after exiting
fastboot. Autoboot should implement a boot script such as "fastboot; mmc
read <...>; bootm" to fully implement the fastboot continue function.
Signed-off-by: Rob Herring <[email protected]>
Tested-by: Lukasz Majewski <[email protected]>
[TestHW: Exynos4412-Trats2]