mvebu: backport a kernel irq fix for setting IRQ affinity

The IRQ controller can only set the affinity to a single CPU. Update the
mask in the controller data.

Suggested-by: Sebastian Gottschall <s.gottschall@dd-wrt.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/mvebu/patches-4.9/130-irqchip-armada-xp-backport.patch

@@ -0,0 +1,17 @@
+Backport a change that updates the effective affinity mask. The Armada IRQ
+controller only supports setting the affinity to a single CPU, and the IRQ
+subsystem needs to know about that.
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+--- a/drivers/irqchip/irq-armada-370-xp.c
++++ b/drivers/irqchip/irq-armada-370-xp.c
+@@ -251,6 +251,8 @@ static int armada_xp_set_affinity(struct
+ 	writel(reg, main_int_base + ARMADA_370_XP_INT_SOURCE_CTL(hwirq));
+ 	raw_spin_unlock(&irq_controller_lock);
+ 
++	cpumask_copy(irq_data_get_affinity_mask(d), cpumask_of(cpu));
++
+ 	return IRQ_SET_MASK_OK;
+ }
+ #endif