ArmPlatformPkg/ArmPlatformLib: Move the UEFI memory partionning to MemoryInitPei

Formerly, each platform was responsible to declare the location of its UEFI memory
region (used by PEI and DXE Foundations).
The ArmPlatformLib was also declaring every region of its partitionned system memory
with a System Resource HOB.

In this new model, the MemoryInit expects the system memory to be declared with the
PCDs gArmTokenSpaceGuid.PcdSystemMemoryBase/Size.
These PCDs declare the largest continuous DRAM region. Additional regions can be
declared with the ArmPLatformLib function ArmPlatformGetAdditionalSystemMemory().

Now, it is the PEIM that partitions the system memory for every platform. It installs
a region of the size PcdSystemMemoryUefiRegionSize (default 128MB) for the PEI permanent
memory at the top of the DRAM region.
And a region of gArmPlatformTokenSpaceGuid.PcdSystemMemoryFixRegionSize (default 128MB)
is declared at the base of the system memory. This region is used for the allocation that
requires fixed address or have some constraints on their locations.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11481 6f19259b-4bc3-4df7-8a09-765794883524