OvmfPkg: Add basic skeleton for the XenBus bus driver.
    
    This includes Component Name and Driver Binding.
    
    Change in V4:
    - Replace the license by the commonly used file header text.
    - Add brief description for the driver.
    
    Change in V3:
    - enable compilation for Ia32 and Ia32X64
    - fix version (driver binding)
    
    Change in V2:
    - Simple support of controller name.
    - Cleaning up comments, files header.
    - Add Licenses
    - Rename XenbusDxe to XenBusDxe.
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
    
    git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16258 6f19259b-4bc3-4df7-8a09-765794883524