irqchip: Remove header drivers/irqchip/irqchip.h

All drivers using the macro IRQCHIP_DECLARE have been converted to using global
header include/linux/irqchip.h. Local header drivers/irqchip/irqchip.h is now
useless and can be removed.

Signed-off-by: Joel Porquet <joel@porquet.org>
Cc: vgupta@synopsys.com
Cc: monstr@monstr.eu
Cc: ralf@linux-mips.org
Cc: jason@lakedaemon.net
Link: http://lkml.kernel.org/r/2818400.nekF4hg2Ig@joel-zenbook


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>