KabylakeOpenBoardPkg: Fixed system hang caused by MemoryTest.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1550



OS hang due to non-existing memory reported as usable memory.
There are 2 different RVP3 boards and one with 4GB memory down
implementation while another one with 8GB. Since rest of the
configurations are exactly the same, board detection is added
to the same RVP3 BoardInitLib and only SPD policy assigned
differently.

This also fixed below 2 issues:
1. Fixed build failuire when PcdMultiBoardSupport == FALSE.
   (Wrong Pcd TokenSpace used in DxeBoardAcpiTableLib.inf)
2. Always failed to read SPD from DIMM because SpdAddressTable
   policy was not updated properly. Fixed by a notify callback
   when policy PPI installed.

Test: Verified both RVP3 boards can boot to Windows.

Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Signed-off-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>