audio/avrcp: Fix uninitialized variable

This fixes the following error:

profiles/audio/avrcp.c:2847:6: error: variable 'num_of_items' is used
      uninitialized whenever 'if' condition is true
      [-Werror,-Wsometimes-uninitialized]
        if (pdu->params[0] == AVRCP_STATUS_OUT_OF_BOUNDS)
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
profiles/audio/avrcp.c:2857:40: note: uninitialized use occurs here
        media_player_total_items_complete(mp, num_of_items);
                                              ^~~~~~~~~~~~
profiles/audio/avrcp.c:2847:2: note: remove the 'if' if its condition is always
      false
        if (pdu->params[0] == AVRCP_STATUS_OUT_OF_BOUNDS)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
profiles/audio/avrcp.c:2839:23: note: initialize the variable 'num_of_items' to
      silence this warning
        uint32_t num_of_items;
                             ^
                              = 0
diff --git a/profiles/audio/avrcp.c b/profiles/audio/avrcp.c
index 37bc291..70c184b 100644
--- a/profiles/audio/avrcp.c
+++ b/profiles/audio/avrcp.c
@@ -3112,7 +3112,7 @@
 	struct avrcp *session = user_data;
 	struct avrcp_player *player = session->controller->player;
 	struct media_player *mp = player->user_data;
-	uint32_t num_of_items;
+	uint32_t num_of_items = 0;
 
 	if (pdu == NULL)
 		return -ETIMEDOUT;