irqchip: add to the directories part of the IRQ subsystem in MAINTAINERS

Now that the drivers/irqchip/ directory is getting more code, it needs
a maintainer. The obvious maintainer for it is Thomas Gleixner, who is
maintaining the overall IRQ subsystem. So we add drivers/irqchip/ in
the list of directories that are part of the IRQ subsystem.

Signed-off-by: Thomas Petazzoni <[email protected]>
Reviewed-by: Rob Herring <[email protected]>

MAINTAINERS

@@ -4209,6 +4209,7 @@ M:	Thomas Gleixner <[email protected]>
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core
 F:	kernel/irq/
+F:	drivers/irqchip/
 
 IRQ DOMAINS (IRQ NUMBER MAPPING LIBRARY)
 M:	Benjamin Herrenschmidt <[email protected]>