FROMGIT: usb: typec: tcpm: Implement enabling Auto Discharge disconnect support

TCPCI spec allows TCPC hardware to autonomously discharge the vbus
capacitance upon disconnect. The expectation is that the TCPM enables
AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
then automously discharges vbus when the vbus falls below a certain
threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.

Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
is also used a flag to move TCPCI based TCPC implementations into
Attached.Snk/Attached.Src state as mentioned in
Figure 4-15. TCPC State Diagram before a Connection of the
USB Type-C Port Controller Interface Specification.
In such TCPC implementations, setting AutoDischargeDisconnect would
prevent TCPC into entering "Connection_Invalid" state as well.

Bug: 168555244
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20201029063138.1429760-8-badhri@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit f321a02c
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git

 usb-next)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
(cherry picked from commit e9a276bd2a70537eab1b4162cca9b7eeb0f1514a)
(cherry picked from commit a53a13168af75458cc57fe1e7a0e1129562fcd1a)
Signed-off-by: Will McVicker <willmcvicker@google.com>
(cherry picked from commit 303a3291)
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I3e25e9045c335b48cefaddb70329dd4df7e0fd94