ARM: OMAP4: powerdomain: add support for reading prev logic and mem states

On OMAP4, there is no support to read previous logic state
or previous memory state achieved when a power domain transitions
to RET. Instead there are module level context registers.

In order to support the powerdomain level logic/mem_off_counters
on OMAP4, instead use the previous power state achieved (RET) and
the *programmed* logic/mem RET state to derive if a powerdomain lost
logic or did not.

If the powerdomain is programmed to enter RET state and lose logic
in RET state, knowing that the powerdomain entered RET is good enough
to derive that the logic was lost as well, in such cases.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
[paul@pwsan.com: removed dependency on functional power state series for now;
 bumped copyright date]
Signed-off-by: Paul Walmsley <paul@pwsan.com>