[ARM] bcm2835: Make intc, timer, and pm driver self initializing

We use VMM_CLOCKSOURCE_INIT_DECLARE, VMM_CLOCKCHIP_INIT_DECLARE(),
and VMM_HOST_IRQ_INIT_DECLARE() to make timer and intc drivers
self initializing.

This helps us remove arch_clocksource_init(), arch_clockchip_init(),
and arch_host_irq_init() for bcm2835 SOC support.

Also, we start using common device tree based clocking framework
for bcm2835 SOC support.

Signed-off-by: Anup Patel <anup@brainfault.org>