shared.cfg: Check SSDT for both S3/S4 tests

The SSDT shows whether the bios set the suspend status
correctly, so it's another test point for both S3/S4
tests.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
Merge pull request #639 from zhouqt/suspend

shared.cfg: Check SSDT for both S3/S4 tests