usb: pd: Correctly handle SVDM versions

When receiving an SVDM with an unsupported version, we should
still send a response with the highest version we support,
rather than dropping the packet outright. Also update the
outgoing SVDM version field to 1 (2.0) if operating in PD3 mode.

Change-Id: I0bafb619e0ac16bc45064ef699870b0c03b52b47
Signed-off-by: Jack Pham <jackp@codeaurora.org>