MFC 349133 349146 349150: document PCIOCATTACHED

r349133:

pci(4): Document PCIOCATTACHED

Document the PCIOCATTACHED ioctl(2) in the pci(4) manual.
PCIOCATTACHED is used to query if a driver has attached to a PCI.

Reviewed by: bcr, imp
Differential Revision: https://reviews.freebsd.org/D20652

r349146:

pci.4: wordsmith and add missing words

Add missing words after PCI in the description of the PCIOCWRITE and
PCIOCATTACHED ioctls.
Use singular in PCIOCREAD, we only read one register at the time.

Reviewed by: bcr, bjk, rgrimes, cem
Differential Revision: https://reviews.freebsd.org/D20671

r349150:

pci.4: Use plural configuration registers

It is customary to use plural when talking about PCI configure registers.

Reported by: scottl

Merge conflicts manually.