[media] au8522_common: dont EXPORT_SYMBOL(au8522_led_gpio_enable)

This function is only called from within au8522_common.c - mark it static.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>