Revision 233677 broke certain machines.  Specifically, if the firmware/BIOS
assigned conflicting ranges to BARs then leaving the BARs alone could
result in one device stealing mmio accesses intended to go to a second
device.  Prior to 233677 the PCI bus driver attempted to handle this case
by clearing the BAR to 0 depending on BARs based at 0 not decoding (which
is not guaranteed to be true).  Now when a conflicting BAR is detected the
following steps are taken:

 1) If hw.pci.realloc_bars (a new tunable) is enabled (default is enabled),
    then ignore the current BAR setting from the firmware and attempt to
    allocate a fresh resource range for the BAR.

 2) If 1) failed (or was disabled), disable decoding for the relevant
    BAR type (e.g. disable mem decoding for a memory BAR) and emit a
    warning if booting verbose.

Tested by:	Alex Keda <admin@lissyara.su>
MFC after:	1 week
Add some missing arge MDIO hints.

Submitted by:	Luiz Otavio O Souza <loos.br@gmail.com>
MFp4 CH=227440:

  Convert the structures to C99 style initialisation, which makes it
  a lot easier to check that all of them are set and to generate a
  derived template from them.

Sponsored by:	DARPA, AFRL
MFC after:	2 weeks