ALSA: usb-audio: Fix the mixer control range limiting issue

- mixer_ctl_set() function is limiting the volume level
  to particular range. This results in incorrect initial
  volume setting for that device.
- In USB mixer while calculating the dBmin/dBmax values
  resolution factor is hardcoded to 256 which results in
  populating the wrong values for dBmin/dBmax.
- Fix is to use appropriate resolution factor while
  calculating the dBmin/dBmax values.

CRs-Fixed: 515012
Change-Id: I502355af66f850bb65380c27333c3341fa43a947
Signed-off-by: Deepa Madiregama <dmadireg@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 2f8c388..4df74b3 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1037,8 +1037,10 @@
 	/* USB descriptions contain the dB scale in 1/256 dB unit
 	 * while ALSA TLV contains in 1/100 dB unit
 	 */
-	cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256;
-	cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256;
+	cval->dBmin =
+		(convert_signed_value(cval, cval->min) * 100) / (cval->res);
+	cval->dBmax =
+		(convert_signed_value(cval, cval->max) * 100) / (cval->res);
 	if (cval->dBmin > cval->dBmax) {
 		/* something is wrong; assume it's either from/to 0dB */
 		if (cval->dBmin < 0)