audio: hal: Fix segfault invalid memory dereferencing

Initialize the structure to avoid it having garbage value.
Garbage value causes segfault during runtime.

Change-Id: I12699ffe810f57f63f08df2f78c2d94443788cbe
diff --git a/hal/audio_extn/hw_loopback.c b/hal/audio_extn/hw_loopback.c
index 78e4215..c4dbddc 100644
--- a/hal/audio_extn/hw_loopback.c
+++ b/hal/audio_extn/hw_loopback.c
@@ -599,6 +599,9 @@
     /* Use an empty patch from patch database and initialze */
     active_loopback_patch = &(audio_loopback_mod->patch_db.loopback_patch[
                                 audio_loopback_mod->patch_db.num_patches]);
+
+    memset(active_loopback_patch, 0, sizeof(loopback_patch_t));
+
     active_loopback_patch->patch_handle_id = PATCH_HANDLE_INVALID;
     active_loopback_patch->patch_state = PATCH_INACTIVE;
     active_loopback_patch->patch_stream.ip_hdlr_handle = NULL;