ARM: OMAP4/AM33xx: add cm_init / cm_exit calls for AM33xx and OMAP4+

This is needed for expanding the generic CM driver API to include
AM33xx and OMAP4 also.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Tested-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>