SourceLevelDebugPkg: SourceLevelDebugPkg.dsc add UefiCpuLib LibraryClass

SourceLevelDebugPkg: SourceLevelDebugPkg.dsc add UefiCpuLib LibraryClass

In preparation for moving StandardSignatureIsAuthenticAMD to UefiCpuLib
in UefiCpuPkg, SourceLevelDebugPkg/SourceLevelDebugPkg.dsc needs
LibraryClass UefiCpuLib.
LocalApicLib|UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.inf will need
UefiCpuLib LibraryClass.  Likely most "real" platforms will be using
BaseX2XApicLib instance which already required UefiCpuLib.

Cc: Hao A Wu <hao.a.wu@intel.com>
Signed-off-by: Garrett Kirkendall <garrett.kirkendall@amd.com>
Message-Id: <20200622131825.1352-3-Garrett.Kirkendall@amd.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>