PcdPcieResizableBarSupport was added in MdeModulePkg.dec, update
UNI file as the documentation of the PCD.
Cc: Ray Ni <ray.ni@intel.com> Cc: Hao A Wu <hao.a.wu@intel.com> Signed-off-by: Heng Luo <heng.luo@intel.com> Acked-by: Laszlo Ersek <lersek@redhat.com> Acked-by: Hao A Wu <hao.a.wu@intel.com> Reviewed-by: Ray Ni <ray.ni@intel.com>