This patch adds basic support for Analog Device ADGS1408/09 SPI mux
controller.

The device is probed and set to a disabled state. It uses the new mux
controller framework.
Signed-off-by: NMircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: NPeter Rosin <peda@axentia.se>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>