PCI: Correct kernel-doc of pci_vpd_srdt_size(), pci_vpd_srdt_tag()

The kernel-doc comments don't match the arguments, so fix the comments.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>