AMD: Ignore forced shutdown if transitioning
AMD: Ignore forced shutdown if transitioning

Ignore new forced shutdown requests if we're in the process of
transitioning to off already.  Otherwise, the power button press may
turn the system back on again.

BRANCH=None
BUG=b:192463842
TEST=on guybrush, run the battery down to 2% in S0 and observe that
we can successfully enter G3 even when additional
chipset_force_shutdown() commands come through during the transition

Signed-off-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Change-Id: Ie2c83db939fe1cc8b3258903e209cba6394027fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3000849
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Reviewed-by: Rob Barnes <3ced0940a2329ce70499686f01d3d60685ec66ed@google.com>
Commit-Queue: Rob Barnes <3ced0940a2329ce70499686f01d3d60685ec66ed@google.com>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec