Marvell/Cn9130Db: Introduce board support

This patch introduces all necessary components required
for building EDK2 firmware for CN9130-DB setup A.
Because the board is modular and can be extended to support
also CN9131 and CN9132 SoC variants, extract common part into
.dsc.inc file, which will be included by them.

In order to build this variant, '-D CN9130' flag should be added.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>