ALSA: sound/drivers/vx: fix sparse warning: different signedness

Fix this sparse warning:
  sound/drivers/vx/vx_uer.c:301:42: warning: incorrect type in argument 2 (different signedness)

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/drivers/vx/vx_uer.c b/sound/drivers/vx/vx_uer.c
index 0e1ba9b..b0560fec 100644
--- a/sound/drivers/vx/vx_uer.c
+++ b/sound/drivers/vx/vx_uer.c
@@ -103,7 +103,7 @@
  * returns the frequency of UER, or 0 if not sync,
  * or a negative error code.
  */
-static int vx_read_uer_status(struct vx_core *chip, int *mode)
+static int vx_read_uer_status(struct vx_core *chip, unsigned int *mode)
 {
 	int val, freq;