LinuxKPI: pci.h / linux_pci.c rename pci_driver field

Rename the struct pci_driver {} field got the list_head from links
to node as a driver is actually initialsing this to {} which seems
questionable but it will at least make us match the Linux structure
field name.

MFC after: 3 days
Reviewed by: manu, hselasky
Differential Revision: https://reviews.freebsd.org/D32645