ARM: OMAP4: suspend: Program all domains to retention

Remove the FIXME's in the suspend sequence since
we now intend to support system level RET support.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>