irq_domain: correct a minor wrong comment for linear revmap

The revmap type should be linear for irq_domain_add_linear function.
Signed-off-by: NDong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

kernel/irq/irqdomain.c

@@ -248,7 +248,7 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
 EXPORT_SYMBOL_GPL(irq_domain_add_legacy);
 
 /**
- * irq_domain_add_linear() - Allocate and register a legacy revmap irq_domain.
+ * irq_domain_add_linear() - Allocate and register a linear revmap irq_domain.
  * @of_node: pointer to interrupt controller's device tree node.
  * @size: Number of interrupts in the domain.
  * @ops: map/unmap domain callbacks