WhiskeylakeOpenBoardPkg/WhiskeylakeURvp: DSC cleanup

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2243



This change refactors OpenBoardPkg.dsc and OpenBoardPkgPcd.dsc to
consolidate redundant sections and better group file content to
improve maintainability and readability.

The same pattern made in this change for WhiskeylakeURvp is being
applied to all existing board packages in Platform/Intel to improve
overall consistency.

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