ALSA: soc - Fix compile warnings in wm8903.c

Hide annoying uninitialized warnings:
  sound/soc/codecs/wm8903.c:382: warning: ‘reg’ may be used uninitialized in this function
  sound/soc/codecs/wm8903.c:383: warning: ‘shift’ may be used uninitialized in this function
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/soc/codecs/wm8903.c

@@ -379,8 +379,8 @@ static int wm8903_output_event(struct snd_soc_dapm_widget *w,
 	struct wm8903_priv *wm8903 = codec->private_data;
 	struct i2c_client *i2c = codec->control_data;
 	u16 val;
-	u16 reg;
-	int shift;
+	u16 uninitialized_var(reg);
+	int uninitialized_var(shift);
 	u16 cp_reg = wm8903_read(codec, WM8903_CHARGE_PUMP_0);
 
 	switch (w->reg) {