pinctrl: madera: Fixup SPDX headers

GPL-2.0-only is the preferred way of expressing v2 of the GPL, so switch
to that. Remove some redundant copyright notices and correct some
instances where the wrong comment type has been used in header files.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

pinctrl: madera: Add driver for Cirrus Logic Madera codecs

These codecs have a variable number of I/O lines each of which
is individually selectable to a wide range of possible functions.

The functionality is slightly different from the traditional muxed
GPIO since most of the functions can be mapped to any pin (and even
the same function to multiple pins). Most pins have a dedicated
"alternate" function that is only available on that pin. The
alternate functions are usually a group of signals, though it is
not always necessary to enable the full group, depending on the
alternate function and how it is to be used. The mapping between
alternate functions and GPIO pins varies between codecs depending
on the number of alternate functions and available pins.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>