xhci: dbgtty: remove kfifo_out() wrapper

There is no need to check against kfifo_len() before kfifo_out(). Just
ask the latter for data and it tells how much it retrieved. Or returns 0
in case there are no more.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Link: https://lore.kernel.org/r/20240808103549.429349-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jiri Slaby (SUSE)

drivers/usb/host/xhci-dbgtty.c

@@ -24,19 +24,6 @@ static inline struct dbc_port *dbc_to_port(struct xhci_dbc *dbc)
 	return dbc->priv;
 }
 
-static unsigned int
-dbc_send_packet(struct dbc_port *port, char *packet, unsigned int size)
-{
-	unsigned int		len;
-
-	len = kfifo_len(&port->write_fifo);
-	if (len < size)
-		size = len;
-	if (size != 0)
-		size = kfifo_out(&port->write_fifo, packet, size);
-	return size;
-}
-
 static int dbc_start_tx(struct dbc_port *port)
 	__releases(&port->port_lock)
 	__acquires(&port->port_lock)
@@ -49,7 +36,7 @@ static int dbc_start_tx(struct dbc_port *port)
 
 	while (!list_empty(pool)) {
 		req = list_entry(pool->next, struct dbc_request, list_pool);
-		len = dbc_send_packet(port, req->buf, DBC_MAX_PACKET);
+		len = kfifo_out(&port->write_fifo, req->buf, DBC_MAX_PACKET);
 		if (len == 0)
 			break;
 		do_tty_wake = true;