s390/irq: enforce correct irqclass_sub_desc array size

Add a BUILD_BUG_ON() to enforce that irqclass_sub_desc contains the required
number of defined interrupt descriptions and won't be filled up with zeros.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/irq.c

@@ -56,7 +56,7 @@ static const struct irq_class irqclass_main_desc[NR_IRQS_BASE] = {
  * /proc/interrupts.
  * In addition this list contains non external / I/O events like NMIs.
  */
-static const struct irq_class irqclass_sub_desc[NR_ARCH_IRQS] = {
+static const struct irq_class irqclass_sub_desc[] = {
 	{.irq = IRQEXT_CLK, .name = "CLK", .desc = "[EXT] Clock Comparator"},
 	{.irq = IRQEXT_EXC, .name = "EXC", .desc = "[EXT] External Call"},
 	{.irq = IRQEXT_EMS, .name = "EMS", .desc = "[EXT] Emergency Signal"},
@@ -94,6 +94,7 @@ static const struct irq_class irqclass_sub_desc[NR_ARCH_IRQS] = {
 
 void __init init_IRQ(void)
 {
+	BUILD_BUG_ON(ARRAY_SIZE(irqclass_sub_desc) != NR_ARCH_IRQS);
 	init_cio_interrupts();
 	init_airq_interrupts();
 	init_ext_interrupts();