ARM: mvebu: move Armada 370/XP specific definitions to armada-370-xp.h

In preparation to the introduction of the support for additional SoC,
the mvebu/common.h should be clear of Armada 370/XP-specific
definitions. Therefore, move the Armada 370/XP SMP specific
definitions to the armada-370-xp.h file.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>