PCI/VPD: Include post-processing in pci_vpd_find_tag()

Move pci_vpd_find_tag() post-processing from pci_vpd_find_ro_info_keyword()
to pci_vpd_find_tag(). This simplifies function pci_vpd_find_id_string()
that will be added in a subsequent patch.

Link: https://lore.kernel.org/r/fb15393f-d3b2-e140-2643-570d3abd7382@gmail.com


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>