irqchip: bcm2835: Convert to use IRQCHIP_DECLARE macro

This patch converts irq-bcm2835 driver to use the new IRQCHIP_DECLARE and
irqchip_init.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: Simon Arlott <simon@fire.lp0.eu>
Cc: Olof Johansson <olof@lixom.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-rpi-kernel@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>