usb: pd: Reset msgid counters properly

Make sure to reset both Tx and Rx msgid counters when the
protocol layer needs to be reset. This occurs after hard/soft
reset as well as when starting up a new sink or source session.
Put this in a common function pd_reset_protocol().

Change-Id: I643a60a28e6498ca16b6f46293b8aa05eff40266
Signed-off-by: Jack Pham <jackp@codeaurora.org>