MFC r279465,r284558,r285189,r285273:

r279465 (by rstone):

Validate the schema that the PF driver passed to us

r284558 (by brueffer):

Document title should be in CAPS.

r285189 (by pkelsey):

Fix range upper bound for uint32_t and uint64_t, and reformat range
description for uint8_t, uint16_t, uint32_t, and uint64_t.

r285273 (by pkelsey):

Replace use of .Po Pc with the preferred .Pq for single line
enclosures in iovctl.conf(5), iovctl(8), pci(9), and
pci_iov_schema(9).