ASoC: wm8770: Fix wrong number of enum items

wm8770 codec driver defines ain_enum with a wrong number of items.

Use SOC_ENUM_DOUBLE_DECL() macro and it's automatically fixed.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org