ASoC: sta32x: Fix wrong enum for limiter2 release rate

There is a typo in the Limiter2 Release Rate control, a wrong enum for
Limiter1 is assigned.  It must point to Limiter2.
Spotted by a compile warning:

In file included from sound/soc/codecs/sta32x.c:34:0:
sound/soc/codecs/sta32x.c:223:29: warning: ‘sta32x_limiter2_release_rate_enum’ defined but not used [-Wunused-variable]
 static SOC_ENUM_SINGLE_DECL(sta32x_limiter2_release_rate_enum,
                             ^
include/sound/soc.h:275:18: note: in definition of macro ‘SOC_ENUM_DOUBLE_DECL’
  struct soc_enum name = SOC_ENUM_DOUBLE(xreg, xshift_l, xshift_r, \
                  ^
sound/soc/codecs/sta32x.c:223:8: note: in expansion of macro ‘SOC_ENUM_SINGLE_DECL’
 static SOC_ENUM_SINGLE_DECL(sta32x_limiter2_release_rate_enum,
        ^

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: <stable@vger.kernel.org>