PCI/AER: Generalize TLP Header Log reading

PCI/AER: Generalize TLP Header Log reading

Both AER and DPC RP PIO provide TLP Header Log registers (PCIe r6.1 secs
7.8.4 & 7.9.14) to convey error diagnostics but the struct is named after
AER as the struct aer_header_log_regs. Also, not all places that handle TLP
Header Log use the struct and the struct members are named individually.

Generalize the struct name and members, and use it consistently where TLP
Header Log is being handled so that a pcie_read_tlp_log() helper can be
easily added.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ilpo Järvinen <[email protected]>
[bhelgaas: drop ixgbe changes for now, tidy whitespace]
Signed-off-by: Bjorn Helgaas <[email protected]>