On ARM Cortex A9 platforms the external PL310 L2 cache controller
needs to be initialized dependent on the SoC. For instance on Pandaboard
it needs to call the firmware running in TrustZone's secure world,
on i.MX6 it initializes it directly, on other boards it doesn't need
to be initialized at all, because the bootloader already did so.
Therefore, we should implement the PL310 intialization in board specific
code and not in the base class implementation.
Ref #1312
166672fe16