PCI: Fix broken URL for Dell biosdevname

Dell developed a way to consistently name devices, and their last proposal
was accepted under the name biosdevname.  Fix a broken URL to biosdevname
documentation.

Signed-off-by: Naga Venkata Sai Indubhaskar Jupudi <njupudi@ucsc.edu>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>