usb: pd: Update uevent parameters during hard reset

Ensure that a few of the parameters (SELECTED_PDO, REQUESTED_PDO,
RDO) are properly cleared out during hard reset and a uevent
update is sent to notify userspace clients.

Also, don't reset src_cap_id upon disconnect. This makes it a
a monotonically increasing value upon every connection so that
clients can distinguish when a new PD session is established.
Demote it to a u16 in order to have a smaller wraparound (65535).

Change-Id: I622ad1155b3680d3f616d5e9a835d4c6cbca3636
Signed-off-by: Jack Pham <jackp@codeaurora.org>