ASoC: sgtl5000: Fix SMALL_POP bit definition

On a mx28evk with a sgtl5000 codec we notice a loud 'click' sound  to happen
5 seconds after the end of a playback.

The SMALL_POP bit should fix this, but its definition is incorrect:
according to the sgtl5000 manual it is bit 0 of CHIP_REF_CTRL register, not
bit 1.

Fix the definition accordingly and enable the bit as intended per the code
comment.

After applying this change, no loud 'click' sound is heard after playback

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org