clk: ti: check clock type before doing autoidle ops

Code might use autoidle api with clocks not being omap2 clocks,
so check if clock type is really omap2.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>