genirq: Hide irq_cpu_{on,off}line() behind a deprecated option

irq_cpu_{on,off}line() are now only used by the Octeon platform.
Make their use conditional on this plaform being enabled, and
otherwise hidden away.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20211021170414.3341522-4-maz@kernel.org

kernel/irq/Kconfig

@@ -144,3 +144,10 @@ config GENERIC_IRQ_MULTI_HANDLER
 	bool
 	help
 	  Allow to specify the low level IRQ handler at run time.
+
+# Cavium Octeon is the last system to use this deprecated option
+# Do not even think of enabling this on any new platform
+config DEPRECATED_IRQ_CPU_ONOFFLINE
+	bool
+	depends on CAVIUM_OCTEON_SOC
+	default CAVIUM_OCTEON_SOC

kernel/irq/chip.c

@@ -1122,6 +1122,7 @@ void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set)
 }
 EXPORT_SYMBOL_GPL(irq_modify_status);
 
+#ifdef CONFIG_DEPRECATED_IRQ_CPU_ONOFFLINE
 /**
  *	irq_cpu_online - Invoke all irq_cpu_online functions.
  *
@@ -1181,6 +1182,7 @@ void irq_cpu_offline(void)
 		raw_spin_unlock_irqrestore(&desc->lock, flags);
 	}
 }
+#endif
 
 #ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY