audio: derive sound device for concurrent playback usecases

When a new playback usecase has to be started, existing playback
usecases might have to be re-routed (or not) to the new device
based on usecase requirements or h/w limitations
(e.g headphones and speaker sharing the same backend).

This change addresses this requirement by deriving the
new device based on pre-defined cases.

Bug: 31671778
Change-Id: Ic0fd4e8d2c1119e7198dc5bb5e5a51817f0110c1
diff --git a/hal/msm8960/platform.c b/hal/msm8960/platform.c
index d7fc84c..94f4621 100644
--- a/hal/msm8960/platform.c
+++ b/hal/msm8960/platform.c
@@ -1075,11 +1075,11 @@
     return true;
 }
 
-bool platform_can_split_snd_device(snd_device_t in_snd_device __unused,
+int platform_can_split_snd_device(snd_device_t in_snd_device __unused,
                                    int *num_devices __unused,
                                    snd_device_t *out_snd_devices __unused)
 {
-    return false;
+    return -ENOSYS;
 }
 
 bool platform_check_backends_match(snd_device_t snd_device1 __unused,