ARM: mvebu: use the common function for Armada 375 SMP workaround

Use the common function mvebu_setup_boot_addr_wa() introduced in the
commit "ARM: mvebu: Add a common function for the boot address work
around" instead of the dedicated version for Armada 375.

This commit also moves the workaround in the system-controller
module. Indeed the workaround on 375 is really related to setting the
boot address which is done by the system controller.

As a bonus we no longer use an harcoded value to access the register
storing the boot address.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1406120453-29291-5-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>