bindings: python: make vals in gpiod_Line_set_value consistent with other functions

bindings: python: make vals in gpiod_Line_set_value consistent with other functions

Change the vals in gpiod_Line_set_value from a tuple of tuples to just a
tuple. This brings it into line with other vals in the module such as
gpiod_Line_set_config and gpiod_Line_set_direction_output.

The previous usage made the vals equivalent to an args (a tuple of
arguments equivalent to argc,argv in C), as per gpiod_Line_set_flags.

Renaming vals to args in gpiod_Line_set_value was not an option as there
is already an args parameter.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>