Convert use of pointers in functions of virtio to uint64_t in order to make it
platform-independent.

Add casting from pointers (in PCI functions) to uint64_t and vice versa through
uintptr_t.
Signed-off-by: NMarc Marí <marc.mari.barcelo@gmail.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1424812915-25728-2-git-send-email-marc.mari.barcelo@gmail.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>