[media] s5p-tv: Use devm_gpio_request in sii9234_drv.c

devm_gpio_request is a device managed function and will make
error handling and cleanup a bit simpler.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>