uboot-imx

Reserve the top 16 flag bits for architecture-specific use

Add a convention that the generic global_data only occupy the bottom 16 bits
of the flags word, so that there is less chance of a conflict. At present the
x86 flags conflict.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>