ASoC: rt5670: remove duplicate route.

{ "ADC Stereo1 Filter", NULL, "PLL1", is_sys_clk_from_pll }, and
{ "ADC Stereo2 Filter", NULL, "PLL1", is_sys_clk_from_pll }, are
defined twice in the driver.

Signed-off-by: Bard Liao <bardliao@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>