ASoC: rt5663: rt5663_set_jack_detect() can be static

Fixes: 9958e8afbcad ("ASoC: rt5663: Use the set_jack() instead of the export function")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>