Fix incorrect return status in InitializeDebugPortDriver() & DebugPortSupported().

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Tian, Feng <feng.tian@intel.com>
Reviewed-by: Li, Elvin <elvin.li@intel.com>


git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@15217 6f19259b-4bc3-4df7-8a09-765794883524