TTY: irq: Remove IRQF_DISABLED

Since commit [e58aa3d2: genirq: Run irq handlers with interrupts disabled],
We run all interrupt handlers with interrupts disabled
and we even check and yell when an interrupt handler
returns with interrupts enabled (see commit [b738a50a:
genirq: Warn when handler enables interrupts]).

So now this flag is a NOOP and can be removed.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Acked-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/mpc52xx_uart.c

@@ -274,7 +274,7 @@ static unsigned int mpc5200b_psc_set_baudrate(struct uart_port *port,
 
 static void mpc52xx_psc_get_irq(struct uart_port *port, struct device_node *np)
 {
-	port->irqflags = IRQF_DISABLED;
+	port->irqflags = 0;
 	port->irq = irq_of_parse_and_map(np, 0);
 }