vgaarb: don't pass a cookie to vga_client_register

The VGA arbitration is entirely based on pci_dev structures, so just pass
that back to the set_vga_decode callback.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210716061634.2446357-8-hch@lst.de


Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>