TCPMv2: Use atomic operations for DPM requests
TCPMv2: Use atomic operations for DPM requests

Avoid race conditions between host commands and the PE state machine.

BUG=none
TEST=make buildall
BRANCH=none

Change-Id: I9bb386b6c4e5410152057b2d2d9fd66cdd69441b
Signed-off-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2203841
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

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