Platforms/Marvell: Create MppLib

 - Create Mpp Library, which allows to set MPP on board.
 - Create Platforms/Marvell/Marvell.dec file, which holds PCDs' declaration.
 - Export configuration capabilities via PCDs.
 - Prepare porting guide document

Because GetMppPcd has to be adjusted to possible 8 MPP registers,
although unused, additional PcdChip<X>MppSel are added in order to
satisfy preprocessor demands. For the same reason there are MPP
PCDs for all of 4 possible chips.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jan Dabros <jsd@semihalf.com>
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
5 files changed