ARM: OMAP2+: CM: add common APIs for cm_module_enable/disable

Adds a generic CM driver API for enabling/disabling modules.
The SoC specific implementations are registered through cm_ll_data.

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