tty: st-asc: switch to using devm_gpiod_get()

tty: st-asc: switch to using devm_gpiod_get()

The node pointer in question is not a child node, but the node assigned
to the port device itself, so we should not be using
devm_fwnode_get_gpiod_from_child() [that is going away], but standard
devm_gpiod_get().

To maintain the previous labeling we use gpiod_set_consumer_name() after
we acquire the GPIO.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/20200104202314.GA13591@dtor-ws
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>