SMP support for Armada 375 and 38x

Jason, Andrew, Gregory, Sebastian,

This patch series adds SMP support for the Armada 375 and 38x. Most of the patches are fairly straight-forward, but here is a short overview of what's going on:

* Patches 1, 2, 3 make some preparatory clean-ups. Actually, patches 2 and 3 are not directly related to adding Armada 375 and 38x SMP support, but they are related to the SMP support of Armada XP.

* Patches 4, 5 and 6 add a few bits needed for the SMP support.

* Patch 7 is adding the SMP support itself. Since both Armada 375 and 38x are Cortex-A9, their SMP logic is fairly similar, the only difference being how to define the boot address of the secondary CPU. Therefore, we've used a single smp_operations implementation.

* Patch 8 add a workaround for a SMP booting bug affecting Armada 375 Z1 stepping. It requires using the Crypto SRAM loaded with a few instructions of code as a replacement of the BootROM for booting the secondary processor. For now, the workaround is unconditionally applied on all Armada 375 platforms, but as soon as we get access to more recent platforms, we'll add a mvebu-soc-id based test to only enable the workaround if needed.

* Patch 9 and 10 add the necessary Device Tree bits to enable SMP on Armada 375 and 38x.