MFC: r182108

MFC: r182108

The PCI specifications don't explain the details on how to calculate
the latency based on the Min_Gnt register so use the algorithm found
in OpenSolaris as they probably know how to interpret the value Sun
puts into these registers (previously, the latency calculated for
66MHz was most likely wrong) and for bridges additionally set up the
secondary latency register. Also set up the bridge control register
the way it's done in OpenSolaris. As the latency register don't apply
to PCI-Express and the bridge control setup wasn't tested on sun4v
(besides most likely not being needed), expand the #ifndef SUN4V
accordingly.