usb: typec: tcpm: Respond Wait if VDM state machine is running

Port partner could send PR_SWAP/DR_SWAP/VCONN_SWAP/Request just after it
enters Ready states. This will cause conficts if the port is going to
send DISC_IDENT in the Ready states of TCPM. Set a flag indicating that
the state machine is processing VDM and respond Wait messages until the
VDM state machine stops.

Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Kyle Tso <kyletso@google.com>
Link: https://lore.kernel.org/r/20210114145053.1952756-4-kyletso@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>