CLK: TI: add interface clock support for OMAP3

OMAP3 has interface clocks in addition to functional clocks, which
require special handling for the autoidle and idle status register
offsets mainly.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>