usb: gadget: u_serial: remove some dead code

There is no need to check if "port" is NULL. We already verified that it
is non-NULL. It's a stack variable and can't be modified by a different
thread. Delete this dead code.

Signed-off-by: Dan Carpenter <[e-mail]>
Reviewed-by: Prashanth K <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/function/u_serial.c

···
 		spin_unlock_irqrestore(&serial_port_lock, flags);
 		if (!gserial_wakeup_host(gser))
 			return;
-
-		/* Check if port is valid after acquiring lock back */
 		spin_lock_irqsave(&serial_port_lock, flags);
-		if (!port) {
-			spin_unlock_irqrestore(&serial_port_lock, flags);
-			return;
-		}
 	}
 
 	spin_lock(&port->port_lock);