ASoC: codecs: wsa881x: fix return values from kcontrol put

wsa881x_set_port() and wsa881x_put_pa_gain() currently returns zero eventhough
it changes the value. Fix this, so that change notifications are sent
correctly.

Fixes: a0aab9e1 ("ASoC: codecs: add wsa881x amplifier support")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>