hikey: fastboot: support reboot command
hikey: fastboot: support reboot command

Signed-off-by: Haojian Zhuang <979139d45d262f0480136b0da512e0afa0fe79d3@linaro.org>

96boards/arm-trusted-firmware,vchong/arm-trusted-firmware,96boards/arm-trusted-firmware,vchong/arm-trusted-firmware