[PATCH -next] ALSA: usb-audio: Remove set but not used variable 'first_ch_bits'

[YueHaibing]

Fixes gcc '-Wunused-but-set-variable' warning:

sound/usb/mixer.c: In function 'parse_audio_feature_unit':
sound/usb/mixer.c:1838:28: warning:
 variable 'first_ch_bits' set but not used [-Wunused-but-set-variable]

It never used since 2.6

Signed-off-by: YueHaibing <yuehaib...@huawei.com>
---
 sound/usb/mixer.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index e7d441d..8ad1a24 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1835,7 +1835,7 @@ static int parse_audio_feature_unit(struct mixer_build 
*state, int unitid,
 {
        int channels, i, j;
        struct usb_audio_term iterm;
-       unsigned int master_bits, first_ch_bits;
+       unsigned int master_bits;
        int err, csize;
        struct uac_feature_unit_descriptor *hdr = _ftr;
        __u8 *bmaControls;
@@ -1926,10 +1926,6 @@ static int parse_audio_feature_unit(struct mixer_build 
*state, int unitid,
                break;
 
        }
-       if (channels > 0)
-               first_ch_bits = snd_usb_combine_bytes(bmaControls + csize, 
csize);
-       else
-               first_ch_bits = 0;
 
        if (state->mixer->protocol == UAC_VERSION_1) {
                /* check all control types */