serial: core: Switch to irq_get_nr_irqs()

Use the irq_get_nr_irqs() function instead of the global variable
'nr_irqs'. Prepare for changing 'nr_irqs' from an exported global
variable into a variable with file scope.

Signed-off-by: Bart Van Assche <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: bvanassche

drivers/tty/serial/serial_core.c

@@ -919,7 +919,7 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
 	if (uport->ops->verify_port)
 		retval = uport->ops->verify_port(uport, new_info);
 
-	if ((new_info->irq >= nr_irqs) || (new_info->irq < 0) ||
+	if ((new_info->irq >= irq_get_nr_irqs()) || (new_info->irq < 0) ||
 	    (new_info->baud_base < 9600))
 		retval = -EINVAL;