TCPMv2: PE: Clear PRS request following accept
TCPMv2: PE: Clear PRS request following accept

This CL adds logic to clear any pending DPM_REQUEST_PR_SWAP once we
accept a PRS request from the port partner. This prevents a possible
back to back swap if we want to PRS, but the port partner sends the
request before PRS swap request is generated.

BUG=b:182441965
BRANCH=quiche
TEST=tested quiche with kohaku where quiche attaches in sink
role. This case causes quiche to want to power role swap and causes
the port partner to request a power role swap. Verified that only 1
power role swap occurs.

Signed-off-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@google.com>
Change-Id: I05ee27897d5900e71257d268acd3bd37c8abb787
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2799450
Tested-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Commit-Queue: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>

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