uboot-phytec

arm: global_data: add scu_dev for i.MX8

Add scu_dev for i.MX8, this will be used as a handle
to communite with SCU from A35.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>