treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

mux: adgs1408: Add mod_devicetable.h and remove of_match_ptr

Enables probing via the ACPI PRP0001 route but more is mostly about
removing examples of this that might get copied into new drivers.

Also fixes
drivers/mux/adgs1408.c:112:34: warning: unused variable 'adgs1408_of_match
as has been reported recently.

Fixes: e9e40543ad5b ("spi: Add generic SPI multiplexer")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20200529145726.5708-1-peda@axentia.se
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mux: adgs1408: use the correct MODULE_LICENSE

The file is GPL v2 or later.

Acked-by: Mircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mux: adgs1408: new driver for Analog Devices ADGS1408/1409 mux

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: Mircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>