xl: Fix global pci options

xl: Fix global pci options

commit babde47a3fed "introduce a 'passthrough' configuration option to
xl.cfg..." moved the pci list parsing ahead of the global pci option
parsing.  This broke the global pci configuration options since they
need to be set first so that looping over the pci devices assigns their
values.

Move the global pci options ahead of the pci list to restore their
function.

Fixes: babde47a3fed ("introduce a 'passthrough' configuration option to xl.cfg...")
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>