To enable the usage of virtualization extension related instructions
there is the need to enable the '-mcpu=cortex_a15' compiler flag on
those cpus. To not conflict with other compiler flags (Ref #810) we've
to disable the '-march=arm_v7a' flag.
Ref #1405
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082