oak: enable EC sleep in S3
oak: enable EC sleep in S3

In S3, the EC isn't expecting AP host commands, so it's safe to enable
sleep

BRANCH=none
BUG=none
TEST=Check sleep mask in S0 and S3.
Also check sleep mask after sysjump with AP on and with AP off.

Change-Id: I9dcfe996e8e92e6703d71bbe966cd2447c6b14fe
Signed-off-by: Ben Lok <310171a828df105188e0b545d65d6370e8133283@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/290002
Reviewed-by: Rong Chang <3a05493f7adfb36d203f663b3bc2ba30e9d6284f@chromium.org>

fourier49/BIZ_EC,fourier49/BIZ_EC,fourier49/BIZ_EC,fourier49/BIZ_EC