ARM: OMAP5: Enable arch timer support

Enable Cortex A15 generic timer support for OMAP5 based SOCs.
The CPU local timers run on the free running real time counter clock.

Acked-by: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>