PCI/TPH: Add Steering Tag support

Add pcie_tph_get_cpu_st() to allow a caller to retrieve Steering Tags for a
target memory associated with a specific CPU. The ST tag is retrieved by
invoking PCI ACPI "_DSM to Query Cache Locality TPH Features" method
(rev=0x7, func=0xF) of the device's Root Port device.

Add pcie_tph_set_st_entry() to update the device's Steering Tags. The tags
will be written into the device's MSI-X table or the ST table located in
the TPH Extended Capability space.

Co-developed-by: Eric Van Tassell <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Eric Van Tassell <[email protected]>
Signed-off-by: Wei Huang <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Ajit Khaparde <[email protected]>
Reviewed-by: Somnath Kotur <[email protected]>
Reviewed-by: Andy Gospodarek <[email protected]>

Author: weihuang-amd