pq_alsa.c: fix memory leak after pq_cb_alsa_exit()

Abusing the talloc hierarchical nature may cause some problems,
e.g. on embedded systems with emulated talloc API. Let's release
the memory allocated for a state explicitly.

Change-Id: Ie675a92b1e52a4886dc447af19f65ff5e12a4c40

src/pq_alsa.c

@@ -81,6 +81,7 @@ pq_cb_alsa_exit(void *_state)
 {
 	struct pq_state_alsa *state = _state;
 	snd_pcm_close(state->pcm_handle);
+	talloc_free(state);
 }
 
 static int