irqchip/renesas-irqc: Move over to nested generic chip

Convert the IRQC driver to rely on GENERIC_IRQ_CHIP and
set IRQ_GC_INIT_NESTED_LOCK to enable nested locking.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Cc: jason@lakedaemon.net
Cc: geert+renesas@glider.be
Cc: horms@verge.net.au
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20150928094237.32552.83434.sendpatchset@little-apple
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 27b52c8..67d8027 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -123,6 +123,7 @@
 
 config RENESAS_IRQC
 	bool
+	select GENERIC_IRQ_CHIP
 	select IRQ_DOMAIN
 
 config ST_IRQCHIP