genirq: Provide config option to disable deprecated code

This option covers now the old chip functions and the irq_desc data
fields which are moving to struct irq_data. More stuff will follow.

Pretty handy for testing a conversion, whether something broke or not.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index e0fc6cd..a42c019 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -12,6 +12,10 @@
 config GENERIC_HARDIRQS_NO__DO_IRQ
        def_bool y
 
+# Select this to disable the deprecated stuff
+config GENERIC_HARDIRQS_NO_DEPRECATED
+       def_bool n
+
 # Options selectable by the architecture code
 config HAVE_SPARSE_IRQ
        def_bool n