Modern NXP i.MX series includes several different families, based on
single- or multi-core Arm Cortex-A CPUs. To be able to support more
families within a single target, we split the 'imx' in arch-specific
subtargets, starting with 'cortexa9' for the Cortex-A9 based i.MX 6,
already supported by the original 'imx6' target.
Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>
