ASoC: cq93vc: fix cq93vc_get_regmap build error

49101a25 "ASoC: cq93vc: Remove the set_cache_io() entirely from
ASoC probe" introduced the cq93vc_get_regmap function that has an
obvious build error referring to the 'codec' variable that is not
declared anywhere"

sound/soc/codecs/cq93vc.c: In function 'cq93vc_get_regmap':
sound/soc/codecs/cq93vc.c:157:34: error: 'codec' undeclared (first use in this function)
  struct davinci_vc *davinci_vc = codec->dev->platform_data;
                                  ^

This changes the code to compile again, presumably in the way it was
intended. Not tested.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Xiubo Li <Li.Xiubo@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>