LinuxKPI: pci: cleanup some code and add support for "pcim" (managed)

Restructure some code and add support for various "managed" versions
for PCI resource management.
This is beyond of what iwlwifi needs but some was found with other
wireless drivers and it mostly all goes together.
Add one FreeBSD sepcific feature returning the resource rather than
the handle to allow us to use bus_*() functions in drivers directly.

Sponsored by: The FreeBSD Foundation
MFC after: 10 days
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D30558