ASoC: omap: rx51: Use gpio_request_one to configure tvout_sel gpio

Just slight cleanup to be sync with upcoming change.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>