ASoC: sgtl5000: prevent playback to be muted when terminating concurrent capture

When a sound capture/playback is terminated while a playback/capture
is running, power_vag_event() will clear SGTL5000_CHIP_ANA_POWER in
the SND_SOC_DAPM_PRE_PMD event, thus muting the respective other
channel.

Don't clear SGTL5000_CHIP_ANA_POWER when both DAC and ADC are active
to prevent this.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>