MdeModulePkg: Add generic PciHostBridgeDxe driver.

This driver links to PciHostBridgeLib provided by platform/silicon to
produce PciRootBridgeIo and PciHostBridgeResourceAllocation protocol.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Feng Tian <feng.tian@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19658 6f19259b-4bc3-4df7-8a09-765794883524