ARM: OMAP4: convert to twd_local_timer_register() interface

Add support for the new smp_twd runtime registration interface
to the OMAP4 platforms, and remove the old compile-time support.
Tested on Panda.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>