usb: pd: Send Not_Supported in specific cases

The Not_Supported message was added in PD 3.0. This should
be sent in response to the following:

- Unhandled Unstructured VDM messages
- Unsupported Structured VDM messages; whereas in PD 2.0 these
  are responded with a NAK
- Unhandled messages in the PE_SRC_Ready and PE_SNK_Ready states;
  whereas in PD 2.0 a Reject is sent

Also for unexpected messages (e.g. an unsolicited Accept message
not in response to any request), these need to be handled with
a Soft_Reset.

Change-Id: Ie401c1eac7120ac55242826318c4088b2722d9cb
Signed-off-by: Jack Pham <jackp@codeaurora.org>