Marvell/Armada7k8k: Extend ArmadaSoCDescLib with PP2 information

This patch introduces new library callback (ArmadaSoCDescPp2Get ()),
which dynamically allocates and fills MV_SOC_PP2_DESC structure with
the SoC description of PP2 NICs.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>