OvmfPkg/PlatformPei: log informative message at DEBUG_INFO level
    
    "Platform PEIM Loaded" is an informative message, not an error report. Set
    its debug mask to DEBUG_INFO.
    
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>