uboot-imx

Fix bug: in arch-arm, env_get_char dose not work fine

due to the arm implementation which supposed that U-Boot is in RAM
when we jump to start_armboot

Signed-off-by: gnusercn <gnusercn@gmail.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>