iicbus/mux/pca954x: add support for PCA9546 I2C Switch

Add support for the 4 channel I2C switch from NXP by adding a new
description struct and the list entries. Compared to x=[2345] which
require code to support the INT, for this one no further changes are
needed.

Tested on: WHLE-LS1088A using a SPF+
MFC after: 1 week
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D44009

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

pca954x: harmonize pca9547 and pca954x and add pca9540 support

The two implementations for the pca9548 switch and the pca9547 mux
seemed close enough so we can put them together and with a bit more
abstraction add pca9540 support.

While here apply a bit of consistency in variable and driver naming and
use device_has_property instead of the FDT-only OF_ variant.

This disconnects pca9547 from the build but does not yet delete it.

MFC after: 2 weeks
Reviewed by: mmel (earlier version), avg
Differential Revision: https://reviews.freebsd.org/D35701

iicbus: Remove unused devclass arguments to DRIVER_MODULE.

Remove unused ofw_iicbus_devclass.

Remove unused iicbus_devclass.

pca954x: driver for PCA954x / TCA954x I2C switches

At the moment only PCA9548A is supported and has been tested.

MFC after: 2 weeks