irqchip: irq-armada-370-xp: Use proper return value for ->set_affinity()

The ->set_affinity() hook of 'struct irq_chip' is supposed to return
one of IRQ_SET_MASK_OK or IRQ_SET_MASK_OK_NOCOPY. However, the code
currently simply returns 0. This patch fixes that by using
IRQ_SET_MASK_OK, which tells the IRQ core that it is responsible for
updating irq_data.affinity.

Note that this patch does not cause any change to the compiled code,
as IRQ_SET_MASK_OK has the value 0. This is therefore just a simple
cleanup.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1414151970-6626-4-git-send-email-thomas.petazzoni@free-electrons.comSigned-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-armada-370-xp.c

@@ -265,7 +265,7 @@ static int armada_xp_set_affinity(struct irq_data *d,
 	writel(reg, main_int_base + ARMADA_370_XP_INT_SOURCE_CTL(hwirq));
 	raw_spin_unlock(&irq_controller_lock);
 
-	return 0;
+	return IRQ_SET_MASK_OK;
 }
 #endif