genirq: Provide irq_get_effective_affinity()

Provide an accessor to the effective interrupt affinity mask. Going to be
used to replace open coded fiddling with the irq descriptor.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201210194042.967177918@linutronix.de

include/linux/irq.h

@@ -906,6 +906,13 @@ struct cpumask *irq_data_get_effective_affinity_mask(struct irq_data *d)
 }
 #endif
 
+static inline struct cpumask *irq_get_effective_affinity_mask(unsigned int irq)
+{
+	struct irq_data *d = irq_get_irq_data(irq);
+
+	return d ? irq_data_get_effective_affinity_mask(d) : NULL;
+}
+
 unsigned int arch_dynirq_lower_bound(unsigned int from);
 
 int __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node,