PCI: Return u8 from pci_find_capability() and similar

PCI Capabilities are linked in a list that must appear in the first 256
bytes of config space.  Each capabilities list pointer is 8 bits.

Change the return type of pci_find_capability() and supporting functions
from int to u8 to match the specification.

[bhelgaas: change other related interfaces, fix HyperTransport typos]
Link: https://lore.kernel.org/r/20201129164626.12887-1-puranjay12@gmail.com


Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>