Many PCI controllers' configuration space accesses are memory-mapped and
vary only in address calculation and access checks. There are 2 main
access methods: a decoded address space such as ECAM or a single address
and data register similar to x86. This implementation can support both
cases as well as be used in cases that need additional pre- or post-access
handling.
Add a new pci_ops member, map_bus, which can do access checks and any
necessary setup. It returns the address to use for the configuration space
access. The access types supported are 32-bit only accesses or correct
byte, word, or dword sized accesses.