samus: Add the pause_in_s5 support and fix CPU throttle

These are changes ported from other haswell systems that are
useful in development.  Pause in S5 can be used for power cycle
testing and the CPU throttle is important for runin since there
is no other active throttle methods.

BUG=chrome-os-partner:23449
BRANCH=samus
TEST=emerge-samus chromeos-ec

Change-Id: I8774a466141f2cdc671a5e14705ae29433f94981
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/173838
Reviewed-by: Randall Spangler <rspangler@chromium.org>