alphaplus: Add voice-speaker-2 backend interface

* Switching to voice-speaker with concurrency requires
  the voice-speaker-2 backend to be set up.

Change-Id: Ibc40d57f318a61c337117ecd2c0ea5a604fc1690

audio/audio_platform_info.xml

@@ -182,6 +182,7 @@
         <device name="SND_DEVICE_LGE_OUT_MITS_MELODY_SPEAKER_TEST" backend="speaker" interface="SEC_MI2S_RX"/>
         <device name="SND_DEVICE_LGE_OUT_MITS_CAMCODER_PLAY_SPEAKER_TEST" backend="speaker" interface="SEC_MI2S_RX"/>
         <device name="SND_DEVICE_OUT_VOICE_SPEAKER" backend="speaker" interface="SEC_MI2S_RX"/>
+        <device name="SND_DEVICE_OUT_VOICE_SPEAKER_2" backend="speaker" interface="SEC_MI2S_RX"/>
         <device name="SND_DEVICE_LGE_OUT_VOIP_SPEAKER" backend="speaker" interface="SEC_MI2S_RX"/>
         <device name="SND_DEVICE_LGE_OUT_LOOPBACK_SPEAKER" backend="speaker" interface="SEC_MI2S_RX"/>
         <device name="SND_DEVICE_LGE_OUT_MT_LOOPBACK_SPEAKER" backend="speaker" interface="SEC_MI2S_RX"/>