The implementation was already there but through a private flag "-_e". The patch removes "-_e" support and add "-ec" support. Removing old "-_e" support makes the pci command more clean. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com> Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>