remove "-c 1" and also protect with test for older kernel / alsa

The "-c 1" was simply wrong. The default (-c 0) sound device of
older kernel / alsa has a numid=3 selector for auto vs headphone vs hdmi .
Newer kernel simply has multiple devices. Also, headphone is -c 0 .

$ amixer contents
numid=2,iface=MIXER,name='Headphone Playback Switch'
  ; type=BOOLEAN,access=rw------,values=1
  : values=on
numid=1,iface=MIXER,name='Headphone Playback Volume'
  ; type=INTEGER,access=rw---R--,values=1,min=-10239,max=400,step=0
  : values=-2000
  | dBscale-min=-102.39dB,step=0.01dB,mute=1

TODO: For now, broadly dividing by kernel v4.x vs v5.x is good enough, but
it would be nice to find out when / which kernel /alsa this is relevant.

closes respeaker#240

seeed-voicecard

@@ -150,5 +150,6 @@ fi
 alsactl restore
 
 #Force 3.5mm ('headphone') jack
-amixer -c 1 cset numid=3 1 || true
-
+if [[ "$kernel_ver" =~ ^4\.*$ ]]; then
+    amixer cset numid=3 1 || true
+fi