genirq: Add GENERIC_IRQ_IPI Kconfig symbol

Select this to enable the generic IPI domain support

Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-4-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 3b48dab..3bbfd6a 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -64,6 +64,10 @@
 	bool
 	select IRQ_DOMAIN
 
+# Generic IRQ IPI support
+config GENERIC_IRQ_IPI
+	bool
+
 # Generic MSI interrupt support
 config GENERIC_MSI_IRQ
 	bool