xfree86: Fix potential NULL references to pci_device in platform probe code
This PR fixes several places where a NULL reference and subsequent crash is possible. These are the only cases where
pdev member is used without checking for NULL beforehand.
As to how that exactly happens one of the possibilities is in
xf86platformProbe which does not really ensure that
pdev are actually filled in. If e.g.
platform_find_pci_info fails to match PCI path, then that member will be left as NULL.
Fixes #1044 (closed).