intel_idle: Power traces should trace sleep state entry

intel_idle: Power traces should trace sleep state entry

BZ: 27776

Currently the power traces use the value of dev->last_state
variable which is updated after the sleep state is exited.
Move the traces to before sleep entry, so that the total
time spent in a sleep state can be displayed correclty by
tools like pytimechart.

Change-Id: If518e63a6018fdb7aa552bcdfe5d8f61aa974164
Signed-off-by: John Mathew <john.mathew@intel.com>
Reviewed-on: http://android.intel.com:8080/39420
Reviewed-by: Hogander, Jouni <jouni.hogander@intel.com>
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Tested-by: Martin, LoicX <loicx.martin@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>