drivers/tty/serial: don't use devm_pinctrl_get_select_default() in probe

Since commit ab78029e (drivers/pinctrl: grab default handles from device core),
we can rely on device core for setting the default pins. Compile tested only.

Acked-by: Linus Walleij <linus.walleij@linaro.org> (personally at LCE13)
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>