TBT UFP: Correct TBT UFP VDM ACK timing with mux task
TBT UFP: Correct TBT UFP VDM ACK timing with mux task

When an EnterMode command comes in, the Responder should be in the USB
mode or safe state before configuring its pins to the new mode and
sending an ACK.

However, since our virtual mux ACK sequence may take longer than the
allowed tVDMEnterMode, the best we can do is wait as long as we can
without violating this timing before sending the ACK.

This patch is synced from the brya patch: http://crrev/c/3411537

BRANCH=None
BUG=b:213024508
TEST=build pass

Signed-off-by: Zhuohao Lee <916bf7ddbf0565669e59e3cb2b613381a48066c0@chromium.org>
Change-Id: I5112d031dbdbf8c9667d22c6c20f434f8fd2b1a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3833263
Reviewed-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>
Commit-Queue: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>

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