ASoC: SOF: ipc-msg-injector: Fix reversed if statement

This if statement is reversed.  In fact, the condition can just be
deleted because writing zero bytes is a no-op.

Fixes: 066c6762 ("ASoC: SOF: ipc-msg-injector: Add support for IPC4 messages")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/Yph+T3PpGCdPsEDj@kiliSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/sof-client-ipc-msg-injector.c

@@ -200,16 +200,14 @@ static ssize_t sof_msg_inject_ipc4_dfs_write(struct file *file,
 		return -EFAULT;
 
 	count -= size;
-	if (!count) {
-		/* Copy the payload */
-		size = simple_write_to_buffer(ipc4_msg->data_ptr,
-					      priv->max_msg_size, ppos, buffer,
-					      count);
-		if (size < 0)
-			return size;
-		if (size != count)
-			return -EFAULT;
-	}
+	/* Copy the payload */
+	size = simple_write_to_buffer(ipc4_msg->data_ptr,
+				      priv->max_msg_size, ppos, buffer,
+				      count);
+	if (size < 0)
+		return size;
+	if (size != count)
+		return -EFAULT;
 
 	ipc4_msg->data_size = count;