genirq: Replace dynamic_irq_init/cleanup

Create a new interface and confine it with a config switch which makes
clear that this is just legacy support and not to be used for new code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Tested-by: Tony Luck <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140507154340.574437049@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -637,6 +637,10 @@ int arch_setup_hwirq(unsigned int irq, int node);
 void arch_teardown_hwirq(unsigned int irq);
 #endif
 
+#ifdef CONFIG_GENERIC_IRQ_LEGACY
+void irq_init_desc(unsigned int irq);
+#endif
+
 #ifndef irq_reg_writel
 # define irq_reg_writel(val, addr)	writel(val, addr)
 #endif