ASoc: codecs: wcd9335: Set digital gain range correctly

digital gain range is -84dB min to 40dB max, however this was not
correctly specified in the range.

Fix this by with correct range!

Fixes: 8c4f021d ("ASoC: wcd9335: add basic controls")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>