CorebootPayloadPkg: Allow PciLib instance selection

CorebootPayloadPkg: Allow PciLib instance selection

On old platform without PCIe express support, the PciLib needs to
be mapped to PciLibCf8 instance to make it work.  On new platform
with PCIe express support, the PciLib needs to be mapped to
PciLibPciExpress to allow access to extended PCIe configuration
space. This patch allows to select the PciLib instance between
PciLibCf8 and PciLibPciExpress using the PCIE_BASE macro through
build command line.

Cc: Prince Agyeman <prince.agyeman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Maurice Ma <maurice.ma@intel.com>
Reviewed-by: Prince Agyeman <prince.agyeman@intel.com>