Use pci_vpd_alloc() to dynamically allocate a properly sized buffer and
read the full VPD data into it.

This avoids having to allocate a buffer on the stack, and we don't have to
make any assumptions on VPD size and location of information in VPD.

This is the same as 5119e20f ("sfc: Read VPD with pci_vpd_alloc()"),
just for the falcon chip version.

Link: https://lore.kernel.org/r/2a8d069e-9516-50d8-6520-2614222c8f5f@gmail.comSigned-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>