usb: typec: tcpm: Set in_ams flag when Source caps have been received

usb: typec: tcpm: Set in_ams flag when Source caps have been received

Receiving the first packet in an AMS sequence signals the
beginning of AMS. Set in_ams flag to true when SRC_CAPS are
received during POWER_NEGOTIATION AMS.
This fixes the failure flagged while running TD.PD.SNK.E9
compliance test.

>From Deterministic PD compliance MOI spec:
TD.PD.SNK.E9. GetSinkCap in Place of Accept
Description:
As Provider, the Tester intentionally sends a GetSinkCap message in place
of Accept message and verifies the UUT will send a SoftReset and recover
from the error.
Steps:
a) Run PROC.PD.E1 Bring-up according to the UUT role.
b) The Tester cycles VBus.
c) The Tester sends a Source Capabilities message to the UUT.
d) Upon receipt of a Request message from the UUT, the Tester replies with
   a GoodCRC message.
e) The Tester sends a GetSinkCap message to the UUT.
f) If a SoftReset is not received within 15 ms after the GetSinkCap EOP was
   sent, the test fails.
g) If a SoftReset is received timely, the Tester replies with an Accept
   message.
h) The Tester sends Source Capabilities message to the UUT repeatedly until
   nCapsCount reached or a GoodCRC is received. If nCapsCount reached, the
   test fails.
i) If a Request is not received timely within 30 ms after the GoodCRC EOP
   corresponding to Source Capabilities message was received, the test
   fails.

Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://lore.kernel.org/r/20210202033859.258491-1-badhri@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>