ShellPkg/pci: Fix extended register dumping for MFVC capability
    
    https://bugzilla.tianocore.org/show_bug.cgi?id=355
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
    Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>