ARM: mvebu: Fix the secondary startup for Cortex A9 SoC

During the secondary startup the SCU was assumed to be in normal
mode. It is not always the case, and especially after a kexec. This
commit adds the needed sequence to put the SCU in normal mode.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1414669184-16785-4-git-send-email-gregory.clement@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>