genirq: Fix function documentation of __irq_alloc_descs()

The function got renamed at some point, but the kernel-doc was not updated.
Signed-off-by: Liguang Zhang <zhangliguang@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/1573656093-8643-1-git-send-email-zhangliguang@linux.alibaba.com

kernel/irq/irqdesc.c

@@ -750,7 +750,7 @@ void irq_free_descs(unsigned int from, unsigned int cnt)
 EXPORT_SYMBOL_GPL(irq_free_descs);
 
 /**
- * irq_alloc_descs - allocate and initialize a range of irq descriptors
+ * __irq_alloc_descs - allocate and initialize a range of irq descriptors
  * @irq:	Allocate for specific irq number if irq >= 0
  * @from:	Start the search from this irq number
  * @cnt:	Number of consecutive irqs to allocate.