usb: typec: tcpm: Comply with TryWait.SNK State

According to the spec:
"4.5.2.2.10.2 Exiting from TryWait.SNK State
The port shall transition to Attached.SNK after tCCDebounce if or when VBUS
is detected. Note the Source may initiate USB PD communications which will
cause brief periods of the SNK.Open state on both the CC1 and CC2 pins,
but this event will not exceed tPDDebounce. The port shall transition to
Unattached.SNK when the state of both of the CC1 and CC2 pins is SNK.Open
for at least tPDDebounce."

Bug: 64261058
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Change-Id: I93adafe336449407232d800a8abc625f8c97c6e1