serial: 8520_port: Fix function param documentation

The parameter is named p while the documentation talks about up.
Fix the doc to be in line with the code.

Fixes: 058bc104f7ca ("serial: 8250: Generalize rs485 software emulation")
Suggested-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/8250/8250_port.c

···
 
 /**
  * serial8250_em485_stop_tx() - generic ->rs485_stop_tx() callback
- * @up: uart 8250 port
+ * @p: uart 8250 port
  *
  * Generic callback usable by 8250 uart drivers to stop rs485 transmission.
  */